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06/12/2023, 09:30
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Luciano Rezzolla06/12/2023, 10:00
I will argue that if black holes represent one the most fascinating implications of Einstein’s theory of gravity, neutron stars in binary system are its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of...
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Maulik Parikh06/12/2023, 11:15
Gravity is usually regarded classically, obeying Newton's law or Einstein's equations. Here I will show that, when the gravitational field is treated quantum-mechanically, the classical trajectories of freely falling objects are subject to random fluctuations, or "noise". Intuitively, the fluctuations can be viewed as arising due to the bombardment of the falling object by gravitons. This...
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Surabhi Sachdev06/12/2023, 12:00
We are in the era of gravitational-wave and multi-messenger astronomy. The latest catalog of transient events from LIGO-Virgo-KAGRA contains 90 high-confidence detections from the first three observing runs. The ongoing fourth observing run is yielding a steady stream of events, with public alerts being issued at a rate of approximately 2-3 per week. All observations are believed to originate...
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Anuj Nandi (Space Astronomy Group, ISITE Campus, U. R. Rao Satellite Centre)06/12/2023, 14:15
AstroSat, India's first multi-wavelength space observatory is an unique platform to observe cosmic X-ray sources, especially to probe the strong gravity of 'compact' objects. I will discuss the capabilities of AstroSat and present some interesting results to decipher the environment around the 'compact' objects.
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Hamsa Padmanabhan06/12/2023, 14:15
Mapping the baryonic content of the Universe, especially after the epoch of Cosmic Dawn -- the birth of the first stars and galaxies --- promises rich insights into both astrophysics and cosmology. The technique of intensity mapping (IM) has emerged as a powerful tool to explore this phase of the Universe by measuring the integrated emission from sources over a broad range of frequencies. A...
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Anuradha Gupta (The University of Mississippi)06/12/2023, 14:15
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Sayan Kar (Indian Institute of Technology Kharagpur)06/12/2023, 14:15
In this talk, I will provide a brief overview of regular spacetimes in theories of gravity. In particular, I will primarily review some of the well--known regular black holes and also discuss wormholes and bubble spacetimes. Some recent results, as well as physical effects in such spacetimes will be mentioned. We will end with
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general comments and open questions. -
aru beri (IISER Mohali, India)06/12/2023, 14:45
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Abhishek Jha (Indian Institute of Science)06/12/2023, 14:45
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Banashree Baishya (IIT Guwahati)06/12/2023, 14:45
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Alapati Tharaka Rama Chowdary (Indian Institute of Technology, Bombay)06/12/2023, 14:45
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Bihag Dave (Ahmedabad University)06/12/2023, 14:45
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Mr ABHIJIT TALUKDAR (Gauhati University)06/12/2023, 14:45
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ANSHUL Verma (Indian Institute of Technology - BHU)06/12/2023, 15:00
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Bhupendra Mishra (Nicolaus Copernicus Astronomical Center Warsaw Poland)06/12/2023, 15:00
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Bikash Ranjan Dinda06/12/2023, 15:00
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Mr Anjan Kar (Indian Institute of Technology Kharagpur)06/12/2023, 15:00
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Aman Srivastava06/12/2023, 15:00
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Bikash Chandra Paul (North Bengal University)06/12/2023, 15:00
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Arko Bhaumik (Indian Statistical Institute, Kolkata)06/12/2023, 15:15
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Ashish Narang (Institute of Physics, Bhubaneswar)06/12/2023, 15:15
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Camelia Jana06/12/2023, 15:15
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Andrew Miller06/12/2023, 15:15
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Chandra Shekhar Murmu (Indian Institute of Technology Indore)06/12/2023, 15:15
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Chiranjeeb Singha06/12/2023, 15:15
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Debarun Paul (Indian Statistical Institute, Kolkata)06/12/2023, 15:30
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Ashish Kumar Meena (Ben-Gurion University of the Negev)06/12/2023, 15:30
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Dr Chandrachur Chakraborty06/12/2023, 15:30
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Avinash Kumar Paladi (Indian Institute of Science)06/12/2023, 15:30
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Ms ASTHA KAKKAR (DEPARTMENT OF PHYSICS AND ASTROPHYSICS, UNIVERSITY OF DELHI, DELHI - 110007, INDIA)06/12/2023, 15:30
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Ms Dibya Chakraborty (Graduate students)06/12/2023, 15:30
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Diganta Parai (University of Hyderabad, PDRF)06/12/2023, 15:45
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Mr Ashu Kushwaha06/12/2023, 15:45
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Ms Debika Chowdhury06/12/2023, 15:45
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Ayan Chatterjee (Central University of Himachal Pradesh)06/12/2023, 15:45
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Golam Mortuza Hossain (IISER Kolkata)06/12/2023, 15:45
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AVINASH TIWARI (IUCAA, PUNE)06/12/2023, 15:45
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Bhaskar Biswas (Universität Hamburg)06/12/2023, 16:00
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Dipankar Barman (Indian Institute of Technology Guwahati)06/12/2023, 16:00
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HIMANSHU VERMA (IIT Bombay)06/12/2023, 16:00
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Mr Ayanendu Dutta (Jadavpur University)06/12/2023, 16:00
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Dr Atrideb Chatterjee (Inter-University Centre for Astronomy and Astrophysics)06/12/2023, 16:00
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Dipanshu G (IISER Pune & RRI)06/12/2023, 16:00
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Mr Debanjan Guha Roy (Birla Institute of Technology & Science Pilani, Hyderabad Campus, Secunderabad, Telangana, India)06/12/2023, 16:15
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BALJEET KAUR LOTTE (Siksha 'O' Anusandhan Deemed to be University)06/12/2023, 16:15
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Dipayan Mukherjee (Indian Institute of Science Education and Research Mohali)06/12/2023, 16:15
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Indu Kalpa Dihingia06/12/2023, 16:15
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Ayan Chakraborty (INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI)06/12/2023, 16:15
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Hari K (Indian Institute of Technology, Madras)06/12/2023, 16:15
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Prof.Jasjeet Singh Bagla06/12/2023, 18:00
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KINJALK LOCHAN (IISER Mohali)06/12/2023, 18:30
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Sudipta Sarkar (IIT, Gandhinagar)06/12/2023, 19:00
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Bhal Chandra Joshi (National Centre for Radio Astrophysics, Pune / Indian Institute of Technology, Roorkee India)07/12/2023, 09:30
A rapidly emerging messenger in astrophysics is gravitational waves (GWs). A new window in the GW spectrum was recently opened when emerging evidence for ultra-long wavelength or nanoHertz frequency GWs was reported by four major pulsar timing array experiments (PTAs). These experiments use a collection of widely separated pulsars in the sky to look for a characteristic spectrum and spatial...
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Aseem Paranjape07/12/2023, 10:15
The evolution and growth of the skeleton of the Cosmic Web goes hand-in-hand with the evolution of gas and galaxies in the Universe and intertwines primordial physics (the details of inflation, dark matter and dark energy) with astrophysics (reionization, star formation and the growth of black holes). Untangling this correlated evolution in order to use the Cosmic Web as a cosmological probe...
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Sendhil Raja07/12/2023, 11:30
Gravitational Waves are the periodic stretching and contracting of space-time produced by rotating astrophysical objects possessing a finite quadrupole moment such as binary stars, binary neutron stars, neutron star-black hole binary or black-hole-black-hole binary, etc. A passing gravitational wave will modulate the distance between two inertial test masses albeit by a very miniscule amount....
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Pratika Dayal07/12/2023, 12:15
Over the past decades, observations have established a sample of more than 200 bright Active galactic nuclei (AGN), powered by accretion onto massive black holes, in the first billion years of the Universe. The James Webb Space Telescope has significantly revised this sample by yielding a sample of unexpectedly numerous and large black holes (up to a 100 million solar masses) within the first...
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Koushiki Bhattacharyya (Ahmedabad University)07/12/2023, 14:30
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Fazlu Rahman07/12/2023, 14:30
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Dr Mohammad Kamran (Uppsala University)07/12/2023, 14:30
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Haridev S R07/12/2023, 14:30
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JOSEPH P J (IISER Mohali)07/12/2023, 14:30
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Kaushik Paul (Indian Institute of Technology Madras)07/12/2023, 14:30
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Harkirat Singh Sahota (Indian Institute of Science Education and Research Mohali, India)07/12/2023, 14:45
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Krishnakanta Bhattacharya (Fukushima University)07/12/2023, 14:45
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N Malsawmtluangi07/12/2023, 14:45
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Krishnendu N V07/12/2023, 14:45
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Jyotijwal Debnath07/12/2023, 14:45
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Indrajit Saha (IIT Guwahati, India)07/12/2023, 14:45
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Indranil Chakraborty (Indian Institute of Technology Bombay)07/12/2023, 15:00
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NANDHIDA KRISHNAN P (Ph.d, Department of Physics, Cochin University of Science and Technology)07/12/2023, 15:00
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Kaustubh Gupta (Indian Institute of Science Education and Research Pune)07/12/2023, 15:00
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M. V. S. Saketh (Max Planck institute for gravitational physics, Potsdam (Albert Einstein Institute))07/12/2023, 15:00
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Parthapratim Mahapatra (Chennai Mathematical Institute)07/12/2023, 15:00
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Mr Prantik Sarmah (Indian Institute of Technology Guwahati)07/12/2023, 15:00
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Muhammed Shafeeque (Indian Institute of Technology Guwahati, India)07/12/2023, 15:15
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praveer tiwari (Indian Institute of Technology, Bombay)07/12/2023, 15:15
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Navin Chaurasiya (IUCAA)07/12/2023, 15:15
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Leon Noble (Indian Institute of Technology Indore)07/12/2023, 15:15
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Dr Poulami Dutta Roy (Chennai Mathematical Institute)07/12/2023, 15:15
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Jaffino Stargen D07/12/2023, 15:15
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Mr Nihar Ranjan Ghosh07/12/2023, 15:30
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Raj Patil (Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Humboldt University)07/12/2023, 15:30
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Kabir Chakravarti (CEICO, FZU, Prague)07/12/2023, 15:30
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Priyanka Sarmah (phd student)07/12/2023, 15:30
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Neev Shah07/12/2023, 15:30
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Mahavir Sharma (IIT Bhilai)07/12/2023, 15:30
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Rajendra Prasad Bhatt (Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India.)07/12/2023, 15:45
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Dr Rajibul Shaikh (Seoul National University of Science and Technology)07/12/2023, 15:45
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Nikodem Poplawski07/12/2023, 15:45
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MD RIAJUL Haque (Indian Institute of Technology Madras)07/12/2023, 15:45
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Kajol Paithankar (Indian Institute of Astrophysics, Bengaluru, India)07/12/2023, 15:45
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Nilanjandev Bhaumik (Indian Institute of Science, Bengaluru)07/12/2023, 15:45
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José M Senovilla (University of the Basque Country UPV/EHU)07/12/2023, 16:30
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Floor Broekgaarden (Simons Foundation | Columbia | Johns Hopkins)08/12/2023, 09:30
In this talk I will discuss the challenges and prospects of Gravitational-wave Paleontology: studying massive stars from their `remnants’ as compact object coalescences, with the goal to answer the key questions in gravitational-wave astronomy today: What can we learn from these gravitational-wave sources about the formation, lives, and explosive deaths of massive stars across cosmic time?...
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Sumati Surya08/12/2023, 10:15
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Bindu Bambah (University of Hyderabad)08/12/2023, 10:30
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08/12/2023, 11:45
Einstein’s equations are a set of classical differential equations for gravity with maximum two space-time derivatives. Black holes are some singular solutions to Einstein’s equations. They behave like large thermodynamic objects, indicating that they are actually an ensemble of the quantum states of gravity. Now any consistent quantum completion of Einstein’s theory typically generates...
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Sourav Chatterjee (TIFR, Mumbai)08/12/2023, 14:15
Since the Nobel winning discovery of gravitational waves (GWs) by the LIGO-Virgo-Kagra (LVK) detectors from merging compact object binaries, understanding the various astrophysical formation channels of these sources has come to sharp focus. While qualitatively, the processes involved in producing these astrophysical systems are well understood, cutting-edge research is underway to put better...
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Sk Jahanur Hoque (BITS Pilani, Hyderabad campus)08/12/2023, 14:15
The physics of gravitational waves is well understood for asymptotically flat space-times. Asymptotic flatness presumes a vanishing cosmological constant. However, cosmological observations over the decades have indicated that our universe is undergoing an accelerated expansion, which is most simply modelled by a de Sitter universe or equivalently by a positive cosmological constant. Even a...
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Saurabh Singh08/12/2023, 14:15
Universe has several poorly constrained periods over its evolution. Formation of first stars and galaxies, followed by reionization of the intergalactic medium is one such epoch. Often referred to as "cosmic dawn", observing this period is extremely challenging due to the faint nature of the signals originating from it. The redshifted 21-cm line from neutral hydrogen offers one such...
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Tejaswi Venumadhav (UCSB)08/12/2023, 14:15
Nearly all of the previous gravitational wave (GW) searches in the LIGO-Virgo-Kagra (LVK) data include GW waveforms with only the dominant quadrupole mode, i.e., omitting higher-order harmonics such as the octupole which are predicted by general relativity. We improved our search pipeline by introducing higher harmonics in the GW templates, and downweighting noise transients (“glitches”) to...
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Sashideep Gutti (bits pilani hyderabad campus)08/12/2023, 14:45
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Rakesh Kabir08/12/2023, 14:45
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Mr NUR JAMAN (Centre for Theoretical Physics, Jamia Millia Islamia)08/12/2023, 14:45
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Samir Mandal (Indian Institute of Space Science and Technology)08/12/2023, 14:45
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P.C Lalremruati (Center of Excellence in Space Science India(CESSI), Indian Institute of Science Education and Research(IISER), Kolkata)08/12/2023, 14:45
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Ritik Sharma08/12/2023, 14:45
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Sayak Datta (Max Planck Institute for Gravitational Physics (AEI))08/12/2023, 15:00
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Roshna K (National Institute of Technology Karnataka, Surathkal)08/12/2023, 15:00
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Paulami Majumder (IISER KOLKATA)08/12/2023, 15:00
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Sanjit Debnath (Aryabhatta Research Institute of Observational Sciences (ARIES), INDIA)08/12/2023, 15:00
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Purba Mukherjee (Indian Statistical Institute, Kolkata)08/12/2023, 15:00
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Seema Satin (Indian Institute of Science Education and Research Kolkata)08/12/2023, 15:00
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Dr Prayush Kumar (ICTS-TIFR)08/12/2023, 15:15
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Shilpa Sarkar (Harish Chandra Research Institute (HRI))08/12/2023, 15:15
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Mr Semin Xavier08/12/2023, 15:15
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Ragavendra H V08/12/2023, 15:15
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S SS08/12/2023, 15:15
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Sayantan Ghosh (Indian Institute of Technology Bombay)08/12/2023, 15:15
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Sarvesh Kumar Yadav (Raman Research Institute, Banglore, India)08/12/2023, 15:30
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Dr Rahul Kothari (Indian Institute of Technology, Mandi)08/12/2023, 15:30
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Dr Shalabh Gautam08/12/2023, 15:30
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Soham Bhattacharyya (IIT Madras)08/12/2023, 15:30
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Rahul Nigam08/12/2023, 15:30
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subhadip sau (Jhargram Raj College)08/12/2023, 15:30
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Rituparna Mandal (University of Hyderabad)08/12/2023, 15:45
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Shauvik Biswas (Indian Association for the Cultivation of Science, Kolkata-700032, India.)08/12/2023, 15:45
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456. Gear-up for the Action Replay: Leveraging Lensing for Enhanced Gravitational-Wave Early-WarningSourabh Magare (Inter University Center for Astronomy and Astrophysics)08/12/2023, 15:45
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Sauraj Bharti (IISER Mohali, Punjab 140306, India)08/12/2023, 15:45
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Rajorshi Chandra (Raman Research Institute)08/12/2023, 15:45
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Mr Subhankar Patra08/12/2023, 15:45
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Shabbir Shaikh (Arizona State University)08/12/2023, 16:00
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Rathul nath Raveendran (Indian Association for the Cultivation of Science, Kolkata, India)08/12/2023, 16:00
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sandipan sengupta (IIT Kharagpur, India)08/12/2023, 16:00
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Souvik jana (International Centre for Theoretical Sciences (ICTS))08/12/2023, 16:00
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Shibendu Gupta Choudhury (S. N. Bose National Centre for Basic Sciences)08/12/2023, 16:00
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Dr Surajit Kalita (University of Cape Town)08/12/2023, 16:00
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Dr Soumya Jana (Sitananda College)08/12/2023, 16:15
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David Reitze (California Institute of Technology)08/12/2023, 17:00
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Nissim Kanekar (National Centre for Radio Astrophysics, India)09/12/2023, 09:30
Temporal evolution in low-energy fundamental constants such as the fine structure constant and the proton-electron mass ratio is a generic prediction of theories that attempt to unify the Standard Model of particle physics and general relativity. The exciting possibility of low-energy tests of such unification theories has inspired a number of methods to probe fundamental constant evolution on...
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Archisman Ghosh (Ghent University)09/12/2023, 10:15
Compact binaries observed in gravitational waves (GWs) are standard distance indicators or standard sirens. This has opened up a novel path to measuring cosmological parameters such as the Hubble constant. In this talk we give a brief overview of the current results in this context from the LIGO-Virgo-KAGRA detector network, some of the near-future prospects, and finally move over to the...
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Vikram Rana09/12/2023, 14:30
X-rays are the signatures of the high-energy Universe. The X-ray band probes extreme environments in the Universe, such as those near black holes or the surface of neutron stars. Observations in X-ray energies of the sky provides the opportunity to study such exotic objects in the Universe, allowing the exploration of physical processes in extreme conditions. Many space missions and...
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Loganayagam R. (ICTS-TIFR, Bengaluru)09/12/2023, 14:30
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Nancy Aggarwal (Northwestern University)09/12/2023, 14:30
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Susmita Adhikari (IISER, Pune)09/12/2023, 14:30
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Sulagna Bhattacharya (Tata Institute of Fundamental Research, Mumbai)09/12/2023, 15:00
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Soumya Bhattacharya (S.N.Bose National Center for Basic Sciences)09/12/2023, 15:00
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Tamanjyot Singh (The University of Texas at Dallas)09/12/2023, 15:00
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Mr SUVASHIS MAITY (INDIAN INSTITUTE OF TECHNOLOGY MADRAS)09/12/2023, 15:00
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Sharvari Nadkarni-Ghosh (IIT Kanpur)09/12/2023, 15:00
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Suman Ghosh09/12/2023, 15:00
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Swati Gavas (Indian Institute of Science Education and Research Mohali (IISER-M))09/12/2023, 15:15
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supragyan priyadarshinee09/12/2023, 15:15
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Mr Siddheshwar Kadam (BITS-Pilani Hyderabad Campus India)09/12/2023, 15:15
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Zenia Zuraiq (Indian Institute of Science)09/12/2023, 15:15
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Sree Mahesh Chandran (Indian Institute of Technology Bombay)09/12/2023, 15:15
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Suprovo Ghosh09/12/2023, 15:15
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Swetha Bhagwat (University of Birmingham)09/12/2023, 15:30
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Swastik Bhattacharya (BITS Pilani Hyderabad)09/12/2023, 15:30
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Susmita Jana09/12/2023, 15:30
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Sreejith Nair09/12/2023, 15:30
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Tanima Duary (INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH KOLKATA)09/12/2023, 15:30
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Soumen Nayak09/12/2023, 15:30
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Srijit Bhattacharjee09/12/2023, 15:45
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Sourav Pal (Indian Statistical Institute, Kolkata)09/12/2023, 15:45
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Pritam Banerjee (Indian Institute of Technology Kharagpur)09/12/2023, 15:45
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Mr Tathagata Ghosh (Inter-University Centre for Astronomy and Astrophysics)09/12/2023, 15:45
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Ujjwal Upadhyay09/12/2023, 15:45
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Ms Tabasum Rahnuma (Indian Institute of Science Education and Research, Bhopal)09/12/2023, 15:45
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Suman Pramanick09/12/2023, 16:00
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upala mukherjee09/12/2023, 16:00
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Tanmoy Chakraborty (Indian Association for the Cultivation of Science)09/12/2023, 16:00
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Subhajit Barman (IIT Madras)09/12/2023, 16:00
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Dr Biplob Sarkar (Department of Applied Sciences, School of Engineering, Tezpur University)09/12/2023, 16:00
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Vaishak Prasad (International Centre for Theoretical Sciences - Tata Institute of Fundamental Research)09/12/2023, 16:00
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Tausif Parvez (Indian Institute Of Technology Bombay)09/12/2023, 16:15
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SAMIK MITRA (Indian Institute of Technology Guwahati)09/12/2023, 16:15
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Subhodeep Sarkar (Indian Institute of Information Technology, Allahabad; Centre for Theoretical Physics, Jamia Millia Islamia)09/12/2023, 16:15
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Susobhan Mandal (IIT Bombay)09/12/2023, 16:15
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Yashi Tiwari (Indian Institute of Science, Bangalore, India)09/12/2023, 16:15
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vishal kumar (Indian Institute of Technology Guwahati)09/12/2023, 16:30
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Mayank Pathak09/12/2023, 16:30
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Sucheta Datta (St.Xavier's College (Autonomous), Kolkata, India)09/12/2023, 16:30
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Mr Seshadri Majumder (Indian Institute of Technology, Guwahati)09/12/2023, 16:45
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Prof. Pradyumn Kumar Sahoo (Birla Institute of Technology and Science-Pilani, Hyderabad Campus)
The rising concern in the Hubble constant tension ($H_0$ tension) of the cosmological models motivates the scientific community to search for alternative cosmological scenarios that could resolve the $H_0$ tension. In this regard, we aim to work on a torsion-based modified theory of gravity which is an alternative description to the coherence model. We solve numerically for the Hubble...
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Bhaskar Biswas (Universität Hamburg)
Despite its elegance, the theory of General Relativity is subject to experimental, observational, and theoretical scrutiny to arrive at tighter constraints or an alternative, more preferred theory. In alternative gravity theories, the macroscopic properties of neutron stars, such as mass, radius, tidal deformability, etc. are modified. This creates a degeneracy between the uncertainties in the...
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Sarvesh Kumar Yadav (Raman Research Institute, Banglore, India)
Observations of the Cosmic Microwave Background (CMB) radiation have made significant contributions to our understanding of cosmology. While temperature observations of the CMB have greatly advanced our knowledge, the next frontier lies in detecting the elusive B-modes and obtaining precise reconstructions of the CMB's polarized signal in general. In anticipation of proposed and upcoming CMB...
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Mr Seshadri Majumder (Indian Institute of Technology, Guwahati)
We present the results of a comprehensive long-term spectro-temporal analysis of eight ultra-luminous X-ray sources (ULXs) with the central object being a black hole, using XMM-Newton monitoring of about a decade. Temporal studies reveal the existence of short-term variability in each sources with fractional variance varying in the range of $1.42-27.28$ per cent. Five sources of the sample are...
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Srijit Bhattacharjee
The gravitational memory effect manifests the permanent relative separation between two test masses, initially held at relative rest, upon interaction with the gravitational waves. It is also shown, that this memory effect is related to the BMS symmetries that emerge at the asymptotic region of spacetimes where the test masses are placed. A similar effect can be obtained near the horizon of...
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Dr Rahul Kothari (IIT Mandi)
We give a new geometrical interpretation of HI intensity mapping foreground filters in harmonic space, for both single-dish and interferometer mode surveys. We derive the foreground-filtered HI auto power spectrum and then extend this to the cross-power spectrum of HI with CMB lensing. Foreground filtering leads to a loss of isotropy in Fourier space, resulting in harmonic space non-diagonal...
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Sanjay Pant (IIT ROPAR)
We perform a holographic study to estimate the effect of backreaction on the correlation between two subsystems forming the thermofield double (TFD) state. Each of these subsystems is described as a strongly coupled large-Nc thermal field theory, and the backreaction imparted to it is sourced by the presence of a uniform distribution of heavy static quarks. The TFD state we consider here...
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Swati Gavas (Indian Institute of Science Education and Research Mohali (IISER-M))
We use cosmological N-body simulations to study a local Hubble constant measurement and study the uncertainty introduced by our lack of peculiar velocities. We consider observers to be located in dark matter halos and target galaxies to be distributed amongst dark matter halos. We average over all observers. Our findings show a trend where local measurements have a significant dispersion...
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Johann Fernandes
Intermediate mass black holes (IMBH) with mass ranges between $100 M_\odot$ to $10^5 M_\odot$ provide a missing link between stellar mass and supermassive black holes. Understanding them provides an insight into galaxy formation as they are considered to be the precursors of supermassive black holes. The high mass of IMBH binaries leads to a short gravitational wave signal duration and...
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Indranil Chakraborty (Indian Institute of Technology Bombay)
A permanent offset caused by the passage of gravitational waves, known as the memory effect, is under active research in both theoretical and observational aspects of gravitational physics. Due to its relation to asymptotic symmetries and soft theorems, the memory effect has received considerable attention for asymptotically flat spacetimes in general relativity (GR). As a result, the memory...
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Mr Mohit Raj Sah (Tata Institute of Fundamental Research, Mumbai)
The astrophysical Stochastic Gravitational Wave Background (SGWB) is the superposition of all the compact binary merger events that go undetected as individual events along with other sources such as supernovae, magnetars, etc. The individual gravitational wave (GW) signals from these events vary over time, depending on the source parameters. The timescale of the individual events along with...
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Mr Suman Pramanick (Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur)
The light-cone (LC) effect arises from the cosmological evolution of the redshifted 21-cm signal along an observer's line of sight (LoS), which is the frequency axis. It is particularly pronounced during the Epoch of Reionization (EoR) when the mean neutral hydrogen fraction (x_HI) and statistical properties change rapidly. The 3D power spectrum only quantifies the ergodic part of the signal...
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M. S. Sūryan Śivadās (Department of physics, Cochin university of science and technology)
The count-in-cells (CIC) is a one point spatial statistic that is used to describe the spatial distribution of galaxies in the Universe. Besides the computational simplicity, it can be modelled theoretically to allow estimation of the parameters describing the large-scale structure of the Universe, such as the $\sigma_8$ and bias. In this work, we measure the galaxy CIC distribution at high...
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Swetha Bhagwat (University of Birmingham)
Binary black hole mergers produce a remnant black-hole in a perturbed state. This then relaxes to form a stable Kerr black hole by emitting gravitational waves, which we call as the ringdown. Ringdowns contain imprints of both strong field linear and non-linear dynamics predicted by the general theory of relativity. Traditionally, we have been using ringdown to test strong-field linear...
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Samanwaya Mukherjee (IUCAA, Pune)
Being subject to the tidal field of its companion, each component of a coalescing binary suffers a slow change in its mass (tidal heating) and spin (tidal torquing) during the inspiral and merger. For black holes, these changes are associated with the energy and angular momentum fluxes down their horizons. This effect modifies the inspiral rate of the binary, and consequently, the phase and...
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Sourav Pal (Indian Statistical Institute, Kolkata)
Massive neutrinos are well-known to cause a characteristic suppression in the growth of structures at scales below the neutrino free-streaming length. A detailed understanding of this suppression is essential in the era of precision cosmology we are entering into, enabling us to better constrain the total neutrino mass and possibly probe LCDM cosmological model(s) and beyond. In this talk, I...
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Pradip Kumar Chattopadhyay (Cooch Behar Panchanan Barma University)
In this article, we analyze a class of compact object in spheroidal geometry described by Vaidya–Tikekar model and MIT bag equation of state considering the finite value of strange quark mass $(m_s)$. The maximum mass and radius is evaluated by maximizing the radial sound velocity $(v_r^2)$ at the centre of the star. For monotonically decreasing nature of the sound velocity, it is noted that...
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Abhishek Sharma
LISA (Laser Interferometer Space Antenna) a planned space-based gravitational wave observatory to be launched in 2034 will be capable of detecting gravitational waves in the milli-Hertz band. Among various sources, LISA will detect the coalescence of massive black hole binaries (MBHBs) with total mass in range $[10^4-10^8] \mathrm{M_\odot}$ up to redshift $\sim$ 10. As such cataclysmic...
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Dr Aru Beri (IISER Mohali)
X-ray binaries, the most luminous galactic objects, harbor the universe's fascinating Neutron Stars (NSs) and Black Holes (BHs). In particular, low-mass X-ray binaries (LMXBs), in which matter from a solar-like companion star falls towards the compact object via an accretion disc, represent excellent laboratories to investigate the motion of matter orbiting nearby these extreme objects. In...
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Rajendra Prasad Bhatt (Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India)
Among various properties of black holes studied so far, their response to an external tidal field remains an especially interesting topic. In our recent work [[arXiv:2306.13627 [gr-qc]][1]], we presented an analytic method for calculating the tidal response function of non-rotating and slowly rotating black holes from the Teukolsky equation in the small frequency and the near horizon limit....
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Dr Shreya Banerjee (Friedrich Alexander University, Erlangen, Germany)
We investigate the cosmological applications of new gravitational scalar-tensor theories and we
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analyze them in the light of H0 tension. In these theories the Lagrangian contains the Ricci scalar
and its first and second derivatives in a specific combination that makes them free of ghosts, thus
corresponding to healthy bi-scalar extensions of general relativity. We examine two specific... -
ANUPAMA B (UNIVERSITY OF HYDERABAD)
The mismatch in the present value of Hubble parameter estimated by Supernova based local measurements and CMB based observations is known as Hubble tension. We attempt to resolve the Hubble tension by considering the curvaton scenario. We show that curvaton influences the Hubble parameter if it gains mass after the inflation and can therefore alleviate the Hubble tension.
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Diganta Parai (University of Hyderabad, PDRF)
In this work we have analytically deduced the frequency dependent expression of conductivity and the band gap energy in AdS4 Schwarzschild background for p-wave holographic superconductors considering Einstein-Yang-Mills theory. We also used the self consistent approach to obtain the expressions of conductivity for different frequency ranges at low temperature. We then compared the imaginary...
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Mr Ashu Kushwaha (Indian Institute of Technology Bombay, India)
At all Universe scales, there is a detectable amount of magnetic field. This observed magnetic field has several probable origins, including the possibility that it was produced during the early Universe. There are several models for primordial magnetogenesis, and if the inflationary background is taken into account, breaking conformal symmetry is required to generate a sufficient amount of...
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Dr Swastik Bhattacharya (BITS Pilani Hyderabad)
Einstein equations projected on Black Hole horizons give rise to the equations of motion of a viscous fluid. This suggests a way to understand the microscopic degrees of freedom on the Black Hole horizon by focusing on the physics of this fluid. In this talk, we shall approach this problem by building a crude model for the Horizon-fluid(HF) corresponding to asymptotically flat Black Holes in...
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Mr Debanjan Guha Roy (Birla Institute of Technology & Science Pilani, Hyderabad Campus, Secunderabad, Telangana, India)
Gravitational wave(GW) astronomy has been maturing rapidly since the first detection of gravitational waves. Already, the current GW detectors have the sensitivity to detect gravitational waves emitted from neutron stars. Next-generation detectors will improve on this, resulting in a golden age of GW astronomy for Neutron Stars(NS). The observed mass of NS is limited to around two times that...
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supragyan priyadarshinee
We present and discuss new families of hairy-charged black hole solutions in asymptotically anti{de Sitter space in three dimensions. The coupled Einstein-Maxwell-scalar gravity system, that carries the coupling $f(\phi)$ between the scalar and Maxwell fields are solved, and exact hairy black hole solutions are obtained analytically. The hairy solutions are obtained for three different...
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Harkirat Singh Sahota (Indian Institute of Science Education and Research Mohali, India)
The uneasiness associated with the notion of a quantum state of a universe presents challenges not only on the interpretational front but on the phenomenological front as well. A reductionist approach that somewhat circumvents this issue is to consider sharply peaked states on the classical trajectory and introducing a quantum-corrected spacetime arising from a quantum gravity model. This...
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Dipankar Barman (Indian Institute of Technology Guwahati)
Quantum entanglement harvesting in the relativistic setup attracted a lot of attention in recent times. Acquiring more entanglement within two qubits may be very desirable to establish fruitful communication between them. On the other hand use of reflecting boundaries in a spacetime has close resemblance to the cavity quantum optomechanical systems. Here, in presence of two reflecting...
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AKHIL U Nair (Birla Institute of Technology & Science Pilani, Hyderabad Campus)
Testing transitivity in quantum field theory is a fundamental aspect of understanding the consistency of the theory and its predictions. In our paper, we considered a vacuum state of the massless scalar field in Minkowski spacetime and two Rindler wedges, Rindler-1 and Rindler-2, separated by a distance. From a set-theoretic view, this setup assumes the picture where the Minkowski spacetime...
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Pritam Banerjee (Indian Institute of Technology Kharagpur)
Tidal disruption of white dwarfs (WD) is an astrophysical transient phenomenon capable of revealing significant information on the presence of intermediate-mass black holes (IMBH). Using hydrodynamical simulations, we explore the observable properties of these astrophysical events. We accurately calculate the fallback rate of the tidal debris during its accretion onto an IMBH. We find the...
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Dr Anuj Nandi (U R Rao Satellite Centre)InvitedOral
AstroSat, India's first multi-wavelength space observatory is an unique platform to observe cosmic X-ray sources, especially to probe the strong gravity aspects of 'compact' objects. I will discuss the capabilities of AstroSat and present some interesting results to decipher the environment around the 'compact' objects.
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Dr Rajeev Kumar Jain
Primordial electromagnetic fields can strongly affect the cosmic evolution of axions and vice versa. We show that if helical electromagnetic fields are coherently produced in the early universe, their remnants source a field velocity to the coupled axions and enhance the relic abundance of axion dark matter. We discuss the implications for the QCD axion and axion-like particles that are...
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Ms Shagun Kaushal
We investigate analytically and numerically the aspects of entanglement for quantum field theoretic systems in the presence of constant-strength background electric and magnetic fields for the cosmological de Sitter spacetime. In particular, we wish to emphasize the role of the magnetic field in the presence of background electric or gravitational fields. Will it oppose the effect of an...
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Surendra Kumar Gour
The observed Universe made up of only baryonic matter indicates that the standard
model of particle physics should be modified to break symmetry between particles and antiparticles. This symmetry breaking is expected to generate unequal number of leptons and antileptons in the reheating era after the inflationary epoch generating the required baryon asymmetry.To model this scenario in the...
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Shantanu Desai (LMU)
The DAMA/LIBRA experiment has been claiming evidence for annual modulation for over 20 years, which they argue is evidence for dark matter WIMP interactions in the detector. However, this result has not been confirmed by any other experiment. We carry out a Bayesian analysis of a search for annual modulation in the DAMA/LIBRA data, which is complementary to the frequentist tests done by the...
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Mr Tathagata Ghosh (Inter-University Centre for Astronomy and Astrophysics)
Gravitational waves (GW) from the inspiral of binary compact objects offer a one-step measurement of the luminosity distance to the event, which is essential for estimating the Hubble constant, $H_{0}$, that characterizes the expansion rate of the Universe. However, unlike binary neutron stars, the inspiral of binary black holes is not expected to be accompanied by electromagnetic radiation...
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Luciano RezzollaPlenaryOral
I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of...
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Dr Rajibul Shaikh (Seoul National University of Science and Technology)
The recent observations of the shadows and images of the supermassive compact objects Sgr A and M87 at the hearts of Our Galaxy and the nearby galaxy M87, respectively, by The Event Horizon Telescope (EHT) collaboration have opened up a new window in observational astronomy to probe and test gravity and fundamental physics in the strong-field regime. It is commonly believed that the...
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Sayak Datta (Max Planck Institute for Gravitational Physics (AEI))
From electromagnetic observations, we know that the supermassive black holes at galactic centers are surrounded by dark and baryonic matter. With the advent of gravitational wave (GW) astronomy, we are poised to probe the details of geometry from where GW gets generated. GWs from binaries containing at least one supermassive black hole will be observed with space-based detector LISA. In such a...
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Krishnakanta Bhattacharya (Fukushima University)
Boundary term and Brown-York (BY) formalism, which is based on the Hamilton-Jacobi principle, are complimentary of each other as the gravitational actions are not, usually, well-posed. In scalar-tensor theory, which is an important alternative to GR, it has been shown that this complementarity becomes even more crucial in establishing the equivalence of the BY quasi-local parameters in the two...
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Ms Sulagna Bhattacharya (Tata Institute of Fundamental Research, Mumbai)
Dark Matter (DM) is ubiquitous and thus has been proposed to be probed by several terrestrial and celestial detectors. DM particles from the galactic halo can accumulate in Neutron Stars (NS) and transmute them into sub-2.5 solar mass black holes (BH) if the DM particles are heavy, stable, and have feeble but sufficient interactions with nucleons. These BHs are named Transmuted Black Holes...
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Dr Ritam Mallick (INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH BHOPAL)
The quest to understand the properties of matter at high density has intrigued physicists for more than a few decades. The problem is complicated, as having a proper theory describing it is challenging. Also, earth-based experiments to probe them have yet to materialize. One of the naturally occurring laboratories where such matter exists is the cores of a neutron star. Recent precise mass and...
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Sashideep Gutti (bits pilani hyderabad campus)
In this paper, we analyze the causal aspects of evolving marginally trapped surfaces in a D dimensional
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spherically symmetric spacetime, sourced by perfect fluid with a cosmological constant. The norm of the
normal to the marginally trapped tube is shown to be the product of lie derivatives of the expansion
parameter of future outgoing null rays along the incoming and outgoing null... -
Muhammed Shafeeque (Indian Institute of Technology Guwahati, India)
The Israel-Carter theorem (famously known as ``no-hair theorem'') puts a restriction on the existence of parameters other than mass, electric charge, and angular momentum of a black hole. On the other hand, Bekenstein showed the possibility of existence of scalar hair by considering a massless conformal scalar field non-minimally coupled to gravity. The Einstein-Maxwell-scalar solution for a...
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Goutam Manna (Prabhat Kumar College, Contai)
The primary objective of this research is to examine the potential for collapse in the generalized emergent Vaidya spacetime, utilizing the theoretical framework of $f(\bar{R}, \bar{T})$ gravity, with a special emphasis on the K-essence theory. In this study, the non-standard Lagrangian of the Dirac-Born-Infeld type is employed to ascertain the emergent metric denoted as $\bar{G}_{\mu\nu}$. It...
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Dr Shalabh Gautam
One of the challenges in numerical relativity is to include future null infinity in the computational domain with a well-posed formulation. Success will not only enable us to evolve any system of astrophysical interest, e.g. binary black holes and extracting the gravitational wave signal at future null infinity, with any desired accuracy, but also help in studying various phenomena of...
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Roshna K (National Institute of Technology Karnataka, Surathkal)
Primordial non-Gaussianity has set strong constraints on models of the early universe. Studies have shown that Loop Quantum Cosmology (LQC), which is an attempt to extend inflationary scenario to planck scales, leads to a strongly scale dependent and oscillatory non-Gaussianity. In particular, the non-Gaussianity function $f_{_{\rm NL}}(k_1,\, k_2,\, k_3)$ generated in LQC, though similar to...
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SUBHASIS MAITI (PhD Student)
In the standard Big Bang model, Reheating follows inflation but precedes Big Bang Nucleosynthesis (BBN), marking the transition from the inflationary epoch to the hot Big Bang. During inflation, the universe expands exponentially due to the inflation field's energy. After inflation, as the field oscillates, it transfers energy to other particles, forming a hot, dense plasma. This phase depends...
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Gopalkrishna Prabhu (Inter-University Centre for Astronomy and Astrophysics)
Galactic spinning compact objects (COs) with non-zero ellipticity are expected to be sources of continuous gravitational waves (CGWs). Certain classes of hypothetical compact objects, such as neutron stars with quark cores (hybrid stars), and quark stars, are thought to have large ellipticities from theoretical considerations. These should enable such COs to produce CGWs detectable by the...
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Soummyadip Basak (ICTS-TIFR, Bangalore)
If a significant fraction of dark matter is in the form of compact objects, they will cause microlensing effects in the gravitational wave signals observable by LIGO and Virgo. From the non-observation of microlensing signatures in the binary black hole events from the first two observing runs and the first half of the third observing run, we constrain the fraction of compact dark matter in...
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Antara Dey
We have done a thorough investigation of the possible effects of interaction between dark matter (DM) and neutrinos during both the reionization and post-reionization epoch. We have constrained the interaction strength using 21 cm Cosmology and found possible deviations from standard, non-interacting $\Lambda$CDM scenario. Comparing the results with the existing constraints from present...
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Ms SUDHAVA Yadav (Malaviya National Institute of Technology, Jaipur)
The era of Reheating is an interesting phase of inflationary Universe and it can be parameterized by various parameters like reheating temperature $T_{\text{re}}$, reheating duration $N_{\text{re}}$ and average equation of state parameter $\overline{\omega }_{\text{re}}$, which can be constrained by observationally viable values of scalar power spectral amplitude $A_{\text{s}}$ and spectral...
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N Malsawmtluangi
The effects of the cosmological phase transitions in the evolution of inflationary gravitational waves are reconsidered and normalized with the data from the late 2021 BICEP/Keck and Planck (BKP) joint data using a quite simple and easily executable method which can be easily modified to include the effects of cosmological events. The resulting energy density spectrum is obtained for the...
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Mr A Thariq (Department of Physics, Chandigarh University)
In this work, we try to compare the cosmological perturbation in the Einstein frame and the Jordan frame for the two-field model. Here we match the metric potentials in both frames to find the equivalence. Further, we evolve the perturbations numerically for selected models.
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Karthik R (Department of Physics, National institute of Technology Karnataka)
The study of cosmological perturbations and quantization during inflation has predominantly focused on the Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. Still, there are very few non-FLRW spacetime cosmological perturbation studies. Among these, the Bianchi I model is one of the simplest anisotropic spacetime models, featuring varying scale factors (a(t)) in orthogonal directions. This...
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Shabbir Shaikh (Arizona State University)
Cross-correlation between weak lensing of the Cosmic Microwave Background (CMB) and weak lensing of galaxies offers a way to place robust constraints on cosmological and astrophysical parameters with reduced sensitivity to certain systematic effects affecting individual surveys. We measure the angular cross-power spectrum between the Atacama Cosmology Telescope (ACT) DR4 CMB lensing and the...
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Jibitesh Dutta (North-Eastern Hill University , Shillong)
Motivated by the effectiveness of $f(Q)$ gravity models in fitting observational data at both background and perturbation levels, our study employs a comprehensive dynamical system analysis to independently validate these findings. We focus on two well-studied $f(Q)$ models, specifically the power-law and exponential variants. Our analysis reveals a matter-dominated saddle point in both cases,...
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Rituparna Mandal (University of Hyderabad)
In this work, we have studied the anisotropic Bianchi type-I cosmological model at late times, taking into account quantum gravitational corrections in the formalism of the exact renormalization group flow of the effective average action for gravity.
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The cosmological evolution equations are derived by including the scale
dependence of Newton’s constant G and cosmological constant Λ. We... -
Indrani Banerjee (NIT, Rourkela)
An exact solution for the bulk five-dimensional geometry is derived for F(R) gravity with nonflat de
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Sitter 3-branes located at the M4 × Z2 orbifold boundaries. The corresponding form of F(R) that leads to
such an exact solution of the bulk metric is derived, which turns out to have all positive integer powers of R.
In such a scenario, the stability issue of the modulus (radion field) is... -
Upala Mukhopadhyay (Jamia Millia Islamia University)
Early data from the James Webb Space Telescope (JWST) has uncovered the
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existence of a surprisingly abundant population of very massive galaxies at extremely high
redshift, which are hard to accommodate within the standard ΛCDM cosmology. We explore
whether the JWST observations may be pointing towards more complex dynamics in the dark
energy (DE) sector. Motivated by the ubiquity of... -
Ms Debika Chowdhury
Recently, several pulsar timing array collaborations announced the first detection of a Stochastic Gravitational Wave Background (SGWB). In this talk, I shall discuss a post-inflationary mechanism, driven by an early scalar-tensor dominated epoch, which is capable of enhancing the size of inflationary tensor fluctuations at frequencies detectable by pulsar timing arrays. The resultant...
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Praveer Tiwari (Indian Institute of Technology, Bombay)
The study of the interior regions of a neutron star is one of the active areas of research
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and gravitational wave astronomy is one of its critical tools. Currently, astronomers
from across the spectrum are detecting different neutron star systems and it has
become essential to consistently combine this information. We perform Bayesian
inference to constrain the equation of state of the... -
Bishnu Das (Department of Physics, Cooch Behar Panchanan Barma University)
A class of relativistic compact objects is analysed in modified Finch-Skea geometry described by modified MIT bag model equation of state of the interior matter. The bag constant B plays an important role in determining the physical features of strange star. In this work we have considered the effect of finite strange quark ($m_{s}≠ 0$) on the stability of quark matter inside a star. We have...
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Mr Arko Bhaumik (Indian Statistical Institute, Kolkata)
We investigate the non-Gaussian three-point cross-correlation function between the primordial curvature perturbation and the primordial magnetic field generated via direct gauge-inflaton coupling, for generic non-standard initial vacua. Among the possible triangular configurations of the resulting cross-bispectrum, we find that the squeezed limit leads to a product form decomposition in terms...
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Shailesh Kumar
Aspects related to black holes surrounded by the astrophysical environment are underappreciated and require profound attention and effort. From an astrophysical viewpoint, we know that dark matter is asserted to be an undetected form of an elementary particle that is not visible, does not interact and contributes almost 27% to the matter-energy of the universe. The development of gravitational...
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Ms Mayusree Das (Indian Institute of Science)
In the past decades, several neutron stars (NSs), particularly pulsars, with mass $M > 2M_\odot$ have been observed. Hence, there is a generic question of the origin of massive compact objects. Here we explore the existence of massive, magnetized, rotating NSs with various equation of states (EoSs) using XNS code, which solves axisymmetric stationary stellar equilibria in general relativistic...
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GOURAB BANERJEE (SAHA INSTITUTE OF NUCLEAR PHYSICS)
Matter inside a neutron star is composed of nucleons in β-equilibrium up to
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2-3 times saturation density(ρ0). The equation of state(EOS) of such matter can
be expressed using iso-scalar and iso-vector nuclear matter parameters (NMPs)
which characterize the symmetric nuclear matter (SNM) and density-dependent
symmetry energy, respectively. The tidal deformation of a neutron star in... -
Rathul nath Raveendran (Indian Association for the Cultivation of Science, Kolkata, India)
In this talk, I discuss the evolution of various measures of quantumness of the curvature perturbation by integrating out the inaccessible entropic fluctuations in the multi-field models of inflation. In particular, I discuss the following measures of quantumness, namely purity, entanglement entropy and quantum discord. The models being considered in this talk are ones that produce large scale...
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Mr Siddheshwar Kadam (BITS-Pilani Hyderabad Campus India)
In this paper, we perform the dynamical system analysis of the cosmological models framed in the extended teleparallel gravity, the $f (T, B)$ gravity. We use the mapping, $f(T, B)=-T+f(T, B)$, and define the dynamical variables to form the autonomous dynamical system. The critical points are obtained in two well-motivated forms of $f (T, B)$, one that involves the logarithmic form of the...
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Afaq Maqsood (Jamia Millia Islamia New Delhi India)
The present work deals with a dynamical systems study of quintessence potentials leading to the present accelerated expansion of the universe. The principal interest is to check for late time attractors which give an accelerated expansion for the universe. Two examples are worked out, namely the exponential and the power-law potential. Furthur we can encountered with the other type of...
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Dr Soumya Jana (Sitananda College)
Black holes with dyonic charges in Einstein-Maxwell-dilaton-axion supergravity theory are revisited in the context of black hole shadows. We consider static as well as rotating (dyonic Kerr-Sen) black holes. The matter stress-energy tensor components, sourced by the Maxwell, axion and dilaton fields satisfy the standard energy conditions. The analytical expressions for the horizon and the...
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Bikash Chandra Paul (North Bengal University)
Abstract : We study evolution of the universe in modified theories of gravity. The dynamics of the universe is explored in the following theories (i) $f(R)= R + \gamma R^2 + \beta R^{\delta}$ where $\beta$, $\gamma$, $\delta$ are arbitrary constants, (ii) $f(R, GB) = R+ f(GB) $, GB is the Gauss-Bonnet term : $GB=R^{\alpha \beta \gamma \delta} R_{\alpha \beta \gamma \delta} -4...
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Mr Swaraj Pratim Sarmah (Dibrugarh University)
Although the sources of ultra-high energy cosmic rays (UHECRs) are unknown, the high-quality data acquired by the most modern CR observatories indicate that these CRs are of extragalactic origin. As the intergalactic media are predicted to be filled with turbulent magnetic fields (TMFs), these intergalactic magnetic fields may profoundly impact how UHECRs travel throughout the expanding...
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Soham Bhattacharyya (IIT Madras)
So far, the post-Newtonian technique has generated spin-less gravitational waveforms of binaries in quasi-circular orbits to a very high degree of precision, or to a high post-Newtonian order. Including spins and eccentricity in the system brings challenges that have not been fully tackled to a high degree of accuracy. The inclusion of spins leads to characteristic effects on the orbital...
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Ayan Chatterjee (Central University of Himachal Pradesh)
Trapped surfaces are the basic building blocks of a black hole region. Marginally trapped surfaces, which are trapped surfaces with vanishing value of the outward null expansion scalar, foliate the null horizon of a black hole in equilibrium. Using the intrinsic geometry of trapped surfaces, it shall be argued that the algebra of classical charges follow a simple algebra. The representation of...
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Lupamudra Sarmah (Indian Institute of Astrophysics, Bangalore)
This abstract is based on our recent papers PRD 105 (2022) 024028 and PRD 107 (2023) 044072. Recent observations of several peculiar over- and under-luminous type Ia supernovae infer indirect evidences for the violation of the Chandrasekhar mass-limit by suggesting the existence of super- and sub-Chandrasekhar limiting mass white dwarfs (WDs). In an attempt to explain these phenomena in the...
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Shamim Haque (Indian Institute of Science Education and Research Bhopal)
Quantum chromodynamics predicts that at high enough temperature/density, hadronic matter (HM) deconfines to quark-gluon matter. it is conjectured that the deconfinement transition from HM to quark matter (QM) takes place at an intermediate density range (a few times nuclear matter density). However, there is no ab-initio calculation, nor are there any earth-based experiments. The only...
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Debarun Paul (Indian Statistical Institute, Kolkata)
$\mathbb{Z}_3$ symmetric dark matter models have demonstrated remarkable potential in addressing various (astro-)particle physics challenges. In this presentation, I will discuss the diverse ways in which this model can successfully explain the different cosmological observations. We have considered two such promising models: semi-annihilating dark matter (SADM) and Co-SIMP $2\rightarrow 3$...
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Ranjan Sharma (Cooch Behar Panchanan Barma University)
We develop a static charged stellar model in $f(R,T)$ gravity where the modification is assumed to be linear in $T$ which is the trace of the energy momentum tensor. The exterior spacetime of the charged object is described by the Reissner-Nordstr\"om metric. The interior solution is obtained by invoking the Buchdahl-Vaidya-Tikekar ansatz, for the metric potential $g_{rr}$, which has a clear...
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NANDHIDA KRISHNAN P (Ph.d, Department of Physics, Cochin University of Science and Technology)
Recently, a novel modification in the conventional area-entropy relation has been introduced by Barrow, as $S=(A/A_{0})^{1+\Delta/2}$, by taking account of the quantum gravitational deformation effects on the black hole's surface. Recent literature has adopted this horizon entropy to the cosmological domain, leading to significant insights. In this line of thought, we formulated the law of...
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Mr Vishal . (IIT Guwahati)
Although the universe presently looks homogenous and isotropic at cosmological scales, there exist small-scale inhomogeneities and anisotropies. In fact, Bianchi had proposed a few anisotropic classical models of the universe which are important in the context of quantum cosmology. In particular, anisotropy is expected to be prominent during the early phase of the universe when it was...
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Koushiki Bhattacharyya (Ahmedabad University)
We study here the unhindered gravitational collapse of spatially homogeneous (SH) scalar fields $\phi$ with a potential $V_{s}(\phi)$, as well as vector fields $\tilde{A}$ with a potential $V_{v}(B)$ where $B=g(\tilde{A},\tilde{A})$ and $g$ is the metric tensor. If the past end-point of a causal geodesic is a singularity, then this singularity is said to be naked. Such a singularity is strong...
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BALJEET KAUR LOTTE (Siksha 'O' Anusandhan Deemed to be University)
The General Theory of Relativity(GTR), Quantum Field Theory(QFT) and Newtonian Quantum Gravity(NQG) are three alternative approaches to study Full Quantum Gravity(FQG). We investigate a system of self-gravtitating fermionic particles with small but significant charges using the NQG model. We derive the equation for ground state energy by adding the energy resulting from charges to the total...
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Golam Hossain
In the study of degenerate compact stars such as neutron stars, general relativistic effects are incorporated by using Tolman-Oppenheimer-Volkoff equations to describe their interior spacetime. However, the equation of states employed in such studies are often computed in flat spacetime. Here, we discuss about the equation of states that are computed in the curved spacetime of these stars. In...
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Md Emanuel Hoque (Saha Institute of Nuclear Physics)
We have investigated the detection probability of continuous Gravitational Wave (CW) signals from the spinning neutron stars in our galaxy across a wide range of their spin frequency. For this purpose, we use observed neutron stars' spin frequencies and spin-down rates, observed with radio telescopes as provided in the Australia Telescope National Facility (ATNF) pulsar catalog. We model the...
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Sk Sohail (Jamia Millia Islamia, New Delhi)
The study investigates the evolution of the global 21 cm temperature, a pivotal cosmological probe for understanding the early Universe, employing a novel approach rooted in scalar field dynamics.In this research, we use scalar field models to understand its impact on 21 cm cosmology, aiming to uncover the unexplored nuances in the temperature fluctuations. Furthermore, we try to understand...
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Mr Suman Kumar Panja (School of Physics, University of Hyderabad)
Quantum gravity has been studied using various approaches and all of these approaches introduce a fundamental length scale in the theory. Non-commutative space-time is an approach which incorporates this fundamental minimum length scale naturally and provides a testing ground to build quantum gravity models. Thus, it is of paramount interest to study how non-commutative space-time will affect...
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R. Prasad (International Centre for Theoretical Sciences, TIFR, Bangalore)
Gravitational waves (GWs) emitted from astrophysical sources can get lensed on their way to Earth, similar to electromagnetic waves. There are claims that detections made by LIGO and Virgo in earlier observational runs show evidence of lensing. Lensing has been invoked to explain the discovered high mass events, the bimodal mass function distribution of black holes, and for the objects in the...
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Dipayan Mukherjee (Indian Institute of Science Education and Research Mohali)
The Jordan and Einstein frame representations of scalar-tensor theories of gravity are mathematically equivalent; however, the cosmological evolutions therein can be drastically different. An interesting example is an expansion-collapse duality -- a continually expanding Einstein frame universe can have a dual Jordan frame description that is always contracting. The scenario eventually runs...
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Abhishek Chowdhuri (IIT Gandhinagar)
In this talk we will explore the late inspiral and then the transition regime to the plunge phase of a secondary, less massive compact object into a more massive deformed Kerr black hole. We will show how one can find fluxes such as the energy and the angular momentum and henceforth use them to infer about their detectibility from a GW standpoint. We also explore how the different deviation...
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ANSHUL Verma (Indian Institute of Technology - BHU)
We delve into the intricacies of the Bianchi-I cosmological model, driven by the intriguing backdrop of anisotropic cosmic microwave background (CMB) observations. In our pursuit to understand the underlying anisotropy of this model, we introduce anisotropic sources into the framework, augmenting the isotropic matter with dust-like dark matter and dark energy in the form of a cosmological...
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Dhritimalya Roy (DEPARTMENT OF PHYSICS, JADAVPUR UNIVERSITY)
In this talk, I will explore a dynamic wormhole solution featuring the Modified Chaplygin Gas (MCG) as the matter at the throat, characterized by an equation of state (EOS): p = Aρ - B/ρ^α.Its global properties, its traversability and the necessary energy conditions to maintain it within the framework of the standard Big Bang cosmological model will be explored.
Further, I will investigate...
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Subhodeep Sarkar (Indian Institute of Information Technology, Allahabad; Centre for Theoretical Physics, Jamia Millia Islamia)
We study linear scalar perturbations of black holes in two-dimensional (2D) gravity models with a particular emphasis on Jackiw-Teitelboim (JT) gravity. We obtain an exact expression of the quasinormal mode frequencies for single horizon black holes in JT gravity and then verify it numerically using the Horowitz-Hubeny method. We shall also consider the dimensionally reduced...
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Dr Rakesh Kabir (University of Delhi)
The detection and parameter estimation of compact binary coalescences (CBC) through the analysis of gravitational wave signals have been revolutionized by the advent of deep learning neural networks. Conventionally, curriculum learning, a method that progressively exposes a neural network to more challenging examples during training, has emerged as the de facto procedure for training these...
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sandipan sengupta (IIT Kharagpur, India)
A dynamical theory of gravity based on an extra dimension of vanishing
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proper length is introduced and explored. Unlike the Kaluza-Klein framework, this formulation is free of an infinite tower of higher eigenmodes, and the fifth dimension cannot be detected in principle. The associated theory emerging from this new extra dimensional formulation in vacuum has a number of implications. We... -
Ashish Kumar Meena (Ben-Gurion University of the Negev)
The first serendipitous detection of a highly magnified star in a spiral galaxy (z=1.49) lensed by a galaxy cluster, MACS1149 (z=0.54), has opened a new window to observe stars at cosmological distances. Since then, several other lensed stars have been detected in HST imaging of various galaxy clusters, and nearly all galaxy clusters observed by JWST revealed lensed stars candidates. Observing...
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Dr Surajit Kalita (University of Cape Town)
This abstract is primarily based on our recent work arXiv:2308.16604. Fast Radio Bursts (FRBs) can be used as a tool to understand different cosmological phenomena because of their distinct features, such as short pulse width, relatively high dispersion measure, etc. On the other hand, over the past decades, researchers have proposed different modified gravity models. In my talk, considering a...
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Mr Nihar Ranjan Ghosh
Ever since Penrose & Simpson contradicted Novikov's prediction that an infalling passenger would emerge into an asymptotically flat universe, there have been a continued interest in predicting the fate of an infalling passenger near the Cauchy horizon (CH) of a Reissner-Nordström (RN) black hole. Poisson & Israel observed that the CH singularity becomes stronger upon considering the...
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Mr HARPREET SINGH (IIT Guwahati)
The Hawking-Wheeler conjecture that the spacetime has a foamy structure at Planckian scales is an attractive feature to be captured in any theory of Quantum Gravity. While Loop Quantum Gravity predicts a discrete geometry at such fundamental scales, String Theory begins with the assumption of stringy nature of all fundamental particles. Both these fundamental theories of Quantum Gravity have...
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Nirmali Das
The distant luminous quasars host supermassive black holes of mass 109 Mʘ thus questioning the presence and formation of the later in the early universe. The formation of massive black holes is studied by the process of Hoyle-Lyttleton-Bondi accretion of self-interacting dark matter (SIDM) onto a 20 $M_⊙$ seed black hole moving with velocity 100 km/s in the SIDM halo. We consider...
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Shauvik Biswas (Indian Association for the Cultivation of Science, Kolkata-700032, India.)
In this work, we present the environmental effects on wormhole geometries residing in a galaxy through a fully relativistic analysis. In particular, we consider two wormhole spacetimes classes: the Damour-Solodukhin wormhole and the braneworld wormhole. While there is no classical matter model for the Damour-Solodukhin wormhole, the braneworld wormhole, on the other hand, is supported by a...
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12. Galaxy-dark matter connection of photometric galaxies from the HSC-SSP Survey using weak lensingNavin Chaurasiya (IUCAA)
In the paradigm of hierarchical structure formation, galaxies are thought to form and evolve inside a potential well environment of 'collisionless' and 'only gravitationally interacting' form of matter; the dark matter halos. These dark halos have formed at the peaks of initial density fluctuations due to gravitational instability and as observations have revealed, are the sites of most of the...
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107. Gear-up for the Action Replay: Leveraging Lensing for Enhanced Gravitational-Wave Early-WarningSourabh Magare (The Inter University Center for Astronomy and Astrophysics)
Pre-merger gravitational-wave (GW) sky-localisation of binary neutron star (BNS) and neutron star black hole (NSBH) coalescence events, would enable telescopes to capture precursors and electromagnetic (EM) emissions around the time of the merger. We propose an astrophysical scenario that could provide early-warning times of hours to days before coalescence with sub-arcsecond localisation,...
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Mr DEBADRI BHATTACHARJEE (COOCH BEHAR PANCHANAN BARMA UNIVERSITY)
A class of new Gravastar solution is presented here following the Mazur and Mottola model in gravitational Bose-Einstein condensate (GBEC) star in the cylindrically symmetric space-time. A stable gravastar with three distinct regions namely, (i) interior de-Sitter space, (ii) intermediate thin shell with a slice of finite length and (iii) exterior vacuum region. The interior region is...
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Susmita Jana
Correspondence between gravity and other fields in gauge theories is yet to be well understood and experimentally verified. The linearity of other gauge theories(such as Maxwell's theory) and the nonlinearity of general relativity make exploring this realm of gravity quite strenuous. The Gertsenshtein-Zeldovich (GZ) effect belongs to this realm, where electromagnetic (EM) waves passing through...
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Nikodem Poplawski
We consider gravitational collapse of a fluid sphere with torsion generated by spin, which forms a black hole.
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We use the Tolman metric and the Einstein-Cartan field equations with a relativistic spin fluid as a source.
We show that gravitational repulsion of torsion prevents a singularity, replacing it with a nonsingular bounce.
Quantum particle creation during contraction prevents shear... -
Ashish Narang (Institute of Physics, Bhubaneswar)
The rate of energy loss and orbital period decay of quasi- stable compact binary systems is a useful tool to constrain theories of gravity. In this talk, we present exact expressions for energy loss and orbital period decay are in three $f (R)$ theories derived using the method of a single vertex graviton emission process from a classical source. After linearising the f (R) action written in...
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BIJENDRA KUMAR VISHVAKARMA (Banaras Hindu University)
An investigation has been done on the gravitational red-shift and blue-shift of photons emitted by time-like geodesics orbiting in the regular Bardeen black hole in the presence of clouds of strings. As the particles/gas are orbiting in a black hole in space-time, they emit light that travels along null geodesics towards the point of detection (observer). In terms of killing vector formalism...
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Soumya Bhattacharya (S.N.Bose National Center for Basic Sciences)
Gravitational wave (GW) memory is studied in the context of a certain class of braneworld wormholes. Unlike other wormhole geometries, this novel class of wormholes do not require any exotic matter fields for its traversability. First, we study geodesics in this wormhole spacetime, in
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the presence of a GW pulse. The resulting evolution of the geodesic separation shows the presence of... -
Mr NUR JAMAN (IISER KOlkata)
In this talk ,I will discuss about the process of induced gravity waves due to large scalar fluctuations in the paradigm of quintessential inflation. Numerically solved the Mukhanov-Sasaki equation for different sets of parameters are used to obtain the power spectra. It is been demonstrated that the induced gravity wave signal generated in this framework can falls within the region of the...
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Ms Anushka Doke (ICTS-TIFR)
We investigate the influence of tidal deformability and strong magnetic fields on the generation of gravitational waves during the inspiral of binary neutron stars in eccentric orbits. Although the current number of identified neutron stars exhibiting strong magnetic fields ($10^{14-15}$ G) remains limited, the maximum allowed magnetic fields in these stars is $10^{18}$ G. Neutron star...
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Dr Surajit Kalita (University of Cape Town)
This abstract is primarily based on my recent paper MNRAS 520 (2023) 3742. Since the discovery of fast radio bursts (FRBs), researchers have proposed several theories and models to explain their characteristics. One of the most recent models takes into account the Gertsenshtein-Zel'dovich (GZ) phenomenon, which suggests that a portion of gravitational radiation is converted into...
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Utkal Keshari Dash (University of Lucknow, Lucknow, Uttar Pradesh, India)
We explore the formulation of Gravitational Waves(GWs) in the modified f(R) gravity model given by f(R)=\frac{R^{1+\delta}}{R^\delta_c}. We introduce the weak field approximation and study polarization of GWs. The Gravitational Waves carry an extra mode of polarization beyond the TT mode for the weak field approximation. We discuss the dependence of the polarization of these waves on the...
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Paulami Majumder (IISER KOLKATA)
In this work, we employ the Frenet-Serret formalism of gyroscopic precession to compute the precession frequency close to the event horizon and naked singularity (NS) for spherically symmetric and axisymmetric spacetime. We aim to determine the possibility of using the gyroscopic precession to distinguish a black hole event horizon from a naked singularity. We show that it is possible to have...
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Anirban Chowdhary
The Halo Occupation Distribution (HOD) has been used as a powerful tool in interpreting quasar clustering and the quasar-halo connection. The HOD formalism provides a complete knowledge of the host halo mass distributions of quasars over a range of redshifts. While extracting host halo distributions of quasar and Active Galactic Nuclei(AGN) from clustering studies, the HOD is assumed to be...
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Dr Prayush Kumar (ICTS-TIFR)
Harmonic coordinates are often used in analytical calculations of the general relativistic binary problem, since they simplify Einstein's equations to a set of quasilinear wave equations. However, numerical relativity simulations of merging binary black holes are commonly performed in different gauges. In this article, we develop a technique to construct harmonic coordinates for binary black...
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Jitumani Kalita (Indian Institute of Technology, Guwahati)
One of the most revolutionary outcomes of Einstein's general theory of relativity is the Black Hole (BH). In 1974 Stephen Hawking showed that BHs can also emit particles called Hawking radiation. The spectrum of the emitted particles is a black body spectrum. Till now we have considered the BH an isolated one and the particle emission spectrum is a Planckian. But we are interested if the BHs...
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Sauraj Bharti (IISER Mohali,SAS Nagar, Punjab 140306, India)
We present our Monte-Carlo simulation of galaxy properties: optical and HI. We use this simulation to study the expected number of direct detections in upcoming surveys (MIGHTEE with MeerKAT and WALLABY with ASKAP). We also study the expected detections in redshifted 21cm line emission with HI stacking. We propose that with these surveys HI stacking can be done in bins with a given range of...
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Tausif Parvez (Indian Institute Of Technology Bombay)
The knowledge of what entered them is completely lost as black holes evaporate. This contradicts the unitarity principle of quantum mechanics and is referred to as the information loss paradox. Understanding the end stages of black hole evaporation is key to resolving this paradox. As a first step, we need to have exact models that can mimic 4-D black holes in General relativity in classical...
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Indu Kalpa Dihingia
To understand the decaying phase of outbursts in black hole (BH) X-ray binaries (BH-XRBs), we performed very long general relativistic magneto-hydrodynamic (GRMHD) simulations of a geometrically thin accretion disk around a Kerr BH with slowly rotating matter injected from outside. We thoroughly studied the flow properties, dynamical behavior of the accretion rate, magnetic flux rate, and jet...
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Mr Somnath Das (University of Hyderabad)
We investigate the higher-order quantum gravity effect on inflationary dynamics within the framework of effective field theory. Our analysis encompasses a broad range of inflationary potentials without specific constraints on their form. We examine the tensor-to-scalar ratio and the running of the spectral indices by considering the generalized inflationary parameters with higher-order quantum...
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Sajal Mukherjee
In this talk, I will discuss the resonance crossing in an Extreme Mass Ratio Inspiral (EMRI). By assuming a charged particle moving in an external homogeneous magnetic field under the electromagnetic self force (ESF), we discuss how it encounters the resonances. In a past work, we compare the resonance timescale between ESF and its adiabatic counterpart, and obtain a qualitative similarity....
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Mr Rahul Shah (Indian Statistical Institute, Kolkata)
Cosmology today, although precise, is perhaps not accurate. The so-called tensions in the standard $\Lambda$CDM model have been cited as a crisis in the field. With no clear evidence of systematical errors, nor a foolproof alternative theory as of now, the crisis is often attributed to the insufficiency of data at hand, that calls for future missions. In this presentation, I would investigate...
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Pratika DayalPlenaryOral
Over the past decades, observations have established a sample of more than 200 bright Active galactic nuclei (AGN), powered by accretion onto massive black holes, in the first billion years of the Universe. The James Webb Space Telescope has significantly revised this sample by yielding a sample of unexpectedly numerous and large black holes (up to a 100 million solar masses) within the first...
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Leon Noble (Indian Institute of Technology Indore)
The fluctuations in the 21-cm radiation emitted by the neutral hydrogen(HI) in the Intergalactic medium(IGM) during different stages of the Epoch of reionization (EoR) is expected to be highly non-Gaussian. The degree of non-Gaussianity varies with the nature of the ionizing sources, state of the IGM and the underlying physical processes within the IGM. One of the crucial observable statistic...
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SAMIK MITRA (Indian Institute of Technology Guwahati)
We study a global, two-dimensional (2D) general relativistic magnetohydrodynamics (GRMHD) simulation of an accreting torus around a non-rotating black hole. Our initial configuration is threaded with a net-vertical magnetic flux. This study investigates the effects of initial field strength onto the disk dynamics. We find that the initial net vertical magnetic field significantly enhances its...
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Shilpa Sarkar (Harish Chandra Research Institute (HRI))
We investigate accretion flows around rotating black holes (BHs) and obtain self-consistent transonic solutions in full general relativistic prescription. The flow is assumed to be viscous and radiative. Viscosity helps in the removal of angular momentum outwards, allowing matter to get accreted inwards. In addition, viscous heat dissipated makes the matter hotter. On the other hand, radiation...
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Mr Pratul Manna (Indian Institute of Technology Madras)
In general relativity, eccentricity is not defined uniquely. Different waveform models rely on gauge-dependent definitions of eccentricity and other orbital elements, which leads to incompatibility between different models. We employ a [recently proposed gauge invariant eccentricity definition][1] to eliminate this ambiguity in our PN-NR comparisons. We also present an eccentric GW model by...
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Deeshani Mitra (Summer Student at U²GRC (UMass-URI Gravity Research Consortium))
In the domain of gravitational wave exploration, the swift prediction of waveforms holds immense importance for real-time and computational scenarios. Our research revolves around the development of efficient surrogate models, encompassing a three-step process to engineer accurate representations of true waveforms. This endeavour brings about transformative enhancements in waveform prediction,...
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Tamanjyot Singh (The University of Texas at Dallas)
Most galaxies host a supermassive black hole (SMBH) at their centers, yet a large fraction of SMBHs are quiescent and only observable through their transient interactions with stellar objects. As a star approaches an SMBH, the tidal gravitational forces can overwhelm the star's self-gravity, resulting in a tidal disruption event (TDE). The disrupted debris accretes onto the black hole,...
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Dr. Abisa Sinha
Space observatory Gaia has prepared a large catalog of 1 billion astronomical objects which consists primarily of stars but also planets, comets, asteroids and quasars among others whose parallaxes are measured instead of distances ($r$). Bailer-Jones (\citet{Bailer-Jones}) established that distance estimation from parallaxes is not trivial once the fractional parallax error is larger...
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Chandra Kant Mishra (IIT Madras)
Post-detection analyses targeting inferences of source properties are often time-consuming and computationally expensive. Assumptions concerning source properties, such as the circularity of binary orbits or the absence of precessing component spins, are routinely made to reduce analysis costs. We shall present a method that may be used to infer the presence (or the lack thereof) of physical...
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Krishnendu N V
We propose a novel test for the quantum nature of astrophysical black holes using gravitational-wave measurements.
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It is known that the black hole absorption and emission spectra will be quantised if the black hole area is quantised. Focusing on the black hole absorption spectra for binary black holes in the pre-merger signal, we quantify the measurability of black hole area quantisation... -
Dr Saikat Chakraborty (The Institute for Fundamental Study "The Tah Poe Academia Institute", Naresuan University)
Minimally Modified Gravity (MMG) theories are gravity theories that differ from Einstein's General Relativity (GR) but do not propagate any additional degree of freedom in the gravity sector. Such theories have given rise to a new direction to the study of modified gravity theories and their cosmological implications are being investigated enthusiastically. In my talk, I will briefly outline...
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Ms Ashmita Rai (BITS Pilani K K Birla Goa Campus)
We use the PLANCK 2018 and the WMAP data to constraint inflation models driven by a scalar field $\phi$ in the presence of the non-minimal scalar-curvature mixing term $\frac{1}{2}\xi R \phi^2$. We consider four distinct scalar field potentials $\phi^p e^{-\lambda\phi},~(1 - \phi^{p})e^{-\lambda\phi},~(1-\lambda\phi)^p$ and $\frac{\alpha\phi^2}{1+\alpha\phi^2}$ to study inflation in the...
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Dr Abhishek Jha (Indian Institute of Science)
The quantum speed limit (QSL) specifies the shortest amount of time required for a quantum system to evolve from an initial to a final state. In this work, we look into QSL for the unitary evolution of neutrinos and antineutrinos in the presence of a gravitational field. Since the transition probabilities between neutrino and antineutrino in the framework of one and two flavors depend on the...
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Mr H Lalrinfela (Department of Physics, Mizoram University)
The Galactic Center (GC) hosting a supermassive black hole, Sgr A* is
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surrounded by a population of S-stars. The orbit of these S-stars is
used as a probe for understanding the nature of gravity in such an
extreme environment. In dynamic interaction between stars and a
supermassive black hole, tidal interaction plays an important role in
determining the fate of the interacting system.... -
Mr Somnath Das (University of Hyderabad)
This presentation introduces a software tool for cosmologists interested in cosmic inflation. Through a user-friendly interface, users input potential functions and visualize how theoretical models of inflation align with observational datasets. Real-time symbolic differentiation calculates key parameters like the scalar spectral index ns and the tensor-to-scalar ratio r, which are...
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Dr Chandrachur Chakraborty
When the fuel of a very massive star is spent, it collapses due to its own gravitational pull and eventually becomes a very small region of arbitrarily high matter density, that is a 'Singularity', where the usual laws of physics may break down. If this singularity is hidden within an event horizon, which is an invisible closed surface from which nothing, not even light, can escape, then we...
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Mayank Pathak (Joint Astronomy Programme, Indian Institute of Science, CV Raman Road, Bangalore, Karnataka, India, 560012)
We explore the behaviour of barotropic and irrotational fluids with a small viscosity under the effect of first-order acoustic perturbations. We discuss, following the extant literature, the difficulties in gleaning an acoustic geometry in the presence of viscosity. In order to obviate various technical encumbrances, when viscosity is present, for an extraction of a possible acoustic geometry,...
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Arbind Pradhan (Department of Applied Sciences, Tezpur University)
GRS 1716-249 is a transient galactic black hole that experienced nine months of outburst activity in 2016–17. During its outbursts, Astrosat observed it at three different epochs with a fair amount of exposure time. We investigate whether quasi-periodic oscillation (QPO) exists and how it has evolved throughout the three epochs. We also explore the energy-dependent nature of QPOs. We model the...
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Mr Xavier Semin
A pivotal question in black hole physics is whether the No-hair theorem is a property of gravity or General Relativity. Associated questions are: Do modified gravity theories allow rotating black hole solutions besides Kerr? If so, what type of modified gravity theories support it, and how are they distinct from the Kerr solution in general relativity? We address some of these questions by...
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Leila Kalhor
We made global fits of the inert Higgs doublet model (IDM) in the light of collider and dark matter search limits and the requirement for a strongly first-order electroweak phase transition (EWPT). These show that there are still IDM parameter spaces compatible with the observational constraints considered. In particular, the data and theoretical requirements imposed favour the hypothesis for...
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Pabitra Tripathy
The first law of black hole mechanics is not physically well-defined because some quantities, such as mass and angular momentum, are defined at infinity, while others, like surface gravity and angular velocity, are defined at the event horizon. Establishing the full law requires traveling back and forth between the horizon and infinity, as well as the knowledge of the entire spacetime, which...
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Mr Sachin Shukla (Indian Institute of Technology Gandhinagar)
LIGO-Aundha is expected to join the network of terrestrial broadband gravitational wave (GW) detectors and begin operations in the early 2030s. We study the impact of this additional detector on the accuracy of determining the direction of incoming transient signals from coalescing binary neutron star sources. Our study involves performing a full Bayesian parameter estimation (PE) over a...
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Aneesha U (IIT Guwahati)
We present the comprehensive analyses of the wide band spectral and timing variabilities of the two BH sources, namely GX 339$-$4 and H 1743$-$322, using AstroSat and NuSTAR observations during $2016-2022$. We observe that both GX 339$-$4 and H 1743$-$322 experienced successful as well as failed outbursts during $2016-2022$. Using long-term MAXI and BAT light curves, we examine the outburst...
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Mr SUVASHIS MAITY (INDIAN INSTITUTE OF TECHNOLOGY MADRAS)
Recently, there have been efforts to examine the contributions to the scalar power spectrum due to the loops arising from the cubic order terms in the action describing the perturbations, specifically in inflationary scenarios that permit a brief epoch of ultra slow roll (USR). A phase of USR inflation leads to significant observational consequences, such as the copious production of...
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Ragavendra H V
Abstract :
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Primordial non-Gaussianity arising from inflationary models is a unique probe of non-trivial dynamics of the inflaton field and its possible interactions with other fields. However, direct observational constraints on the magnitude of non-Gaussianities are relatively weaker compared to those on scalar and tensor power spectra. In my talk, I shall discuss the indirect constraints... -
Mehedi Kalam (Aliah University)
In this paper, we construct a traversable static Lorentzian wormhole in the effective scenario of Loop Quantum Cosmology (LQC), where the field equations are modified due to the ultraviolet (UV) corrections introduced at large space-time curvatures. A stable wormhole can be constructed in the effective scenario without the violation of Null energy condition (NEC) by physical matter at the...
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Sreejith Nair (IIT, Gandhinagar)
Love numbers of compact objects are a valuable tool in probing gravity at its strong field regime and testing for horizons using Gravitational waves. In this talk, we will discuss the definition of Love numbers for compact objects which are asymptotically deSitter. First, we shall discuss a way of defining Love numbers if the spacetime is not asymptotically flat and an appropriate definition...
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Sourav Pal (Indian Institute of Technology, Guwahati)
Magnetic fields are observed throughout the universe on different length scales having different strengths. Galaxies and galaxy clusters have a magnetic field strength of $\sim 10^{-9}~ G$ coherent over a 1KPc scale. We find magnetic fields at $\sim 1 MPc$ scale having a strength of $\sim10^{-16}~ G$ in the intergalactic medium (IGM). Inflationary magnetogenesis is the most profound theory of...
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Koushik Ballav Goswami (Cooch Behar Panchanan Barma University)
In this article we have analyzed a class of strange star described in terms of CFL phase equation of state. The results obtained by considering CFL equation of state is then compared with those obtained from MIT bag model equation of state. It is noted that if we consider the CFL phase equation of state in which the quarks are assumed to form cooper pair, the maximum mass of strange star takes...
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Camelia Jana
We investigate the ejection mechanism in a relativistic, magnetized, viscous, advective accretion flow around a rotating
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black hole (BH) in presence of radiative cooling. Considering the accretion flow to be threaded by toroidal magnetic fields, we self-consistently solve the coupled governing equations that describe the accretion-ejection scenario in terms of the dissipation parameters,... -
Zenia Zuraiq (Indian Institute of Science)
Over the last few years, there has been considerable interest in massive compact stars, specifically neutron stars (NSs) and white dwarfs (WDs). Peculiar over-luminous type Ia supernovae (such as SNLS-03D3bb) and gravitational wave observations (such as GW190814) lend observational support to this idea. These massive compact stars are also prime candidates to fill in the observational mass gap...
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Mr Suraj Maurya (Birla Institute of Technology and Science Pilani Hyderabad Campus)
In this article, we set up a variational problem to arrive at the equation of a maximal hypersurface inside a spherically symmetric evolving trapped region. In the first part of the article, we present the Lagrangian and the corresponding Euler-Lagrange equations that maximize the interior volume of a trapped region that is formed dynamically due to infalling matter in D-dimensions, with and...
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Rahul Nigam
While the area of a black hole is a well defined quantity given by the killing vectors, the enclosed volume depends on the choice of slicing the coordinate system. In this talk we will present the idea of the maximal volume for a family of black holes in 2+1 dimensions. We will demonstrate that the primary contribution to the maximal volume comes from what we call the steady state radius,...
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Ms EMY MONS (CUSAT)
The galaxy Marked Correlation Function (MCF), where the two point correlation function is measured by weighing galaxies with a mark depending on their intrinsic properties, is a powerful statistical tool for probing the environmental dependence of galaxy clustering. We measure and model the MCF of Lyman Break Galaxies from the Subaru HSC-SSP survey[1] in the redshift range 3 to 5 for galaxy...
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Kaustubh Gupta (Indian Institute of Science Education and Research Pune)
Measurements of the Cosmic Microwave Background Radiation indicate the presence of a dipole anisotropy in the sky distribution of temperature fluctuations of the CMB photons. It is believed that the CMB dipole arises because of the earth's motion with respect to the cosmic rest-frame; hence, the strength of the dipole provides an estimate of the earth's speed. Similar measurements recently...
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Kaustubh Gupta (Indian Institute of Science Education and Research Pune)
Dark matter haloes in a given mass range are expected to cluster differently based on secondary halo properties such as concentration or spin, a behaviour known as secondary halo bias. While secondary halo bias has been quantified in simulations, observational uncertainties in halo properties make it difficult to measure the signal in data using only two-point clustering. The $k$-Nearest...
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M. V. S. Saketh (Max Planck institute for gravitational physics, Potsdam (Albert Einstein Institute))
Searches for exotic compact objects (ECOs) from gravitational wave data require a thorough understanding of their signatures during the inspiral and the ringdown. ECOs are motivated by quantum gravity extensions of general relativity and are characterized by the absence of a horizon and partial reflectivity. In the ringdown, which can serve as a fingerprint of an ECO, it is essential to...
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SARBARI GUHA (Associate Professor, Department of Physics, St. Xavier's College (Autonomous), Kolkata 700016, INDIA)
In this paper we study the memory effect produced in pp-wave spacetimes due to the passage of gravitational wave pulses. We assume the pulse profile in the form of a ramp (which may be considered as an appropriate representation of burst gravitational waves), and analyse its effects on the evolution of nearby geodesics. For a ramp profile, we are able to determine analytical solutions of the...
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HIMANSHU VERMA (IIT Bombay)
A detailed analysis is presented of the gravitational microlensing by intervening compact objects of the black hole shadows imaged by the Event Horizon Telescope (EHT). We show how the center, size, and shape of the shadow depend on the Einstein angle relative to the true/unlensed shadow size, and how the location of the lens affects the shift, size, and asymmetry of the black hole shadow due...
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Apratim Ganguly (IUCAA)
GR tests used by the LIGO-Virgo-KAGRA collaboration probes various parts of the gravitational-wave signal. However, a comprehensive understanding of the tests requires accounting for potential biases introduced by unmodeled physical effects like eccentricity, spin precession, or lensing. In this talk, we delve into the intricate influence of microlensing and millilensing on the IMR consistency...
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Prof. Bhupendra Mishra (HRI)
The LIGO/Virgo detections showed unexpected progenitor black hole masses (~66 solar mass). Such black holes with their mass falling in the pair instability mass-gap region seek a new formation channel. We focus on the so-called AGN channel to understand such a puzzling progenitor mass. In this study, we numerically model 3D global MHD accretion flows of embedded black holes within a turbulent...
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Bikash Ranjan Dinda
We study the evolution of the dark energy density parameter and the equation of the state parameter. We also study other relevant background quantities related to the late time cosmic acceleration such as deceleration parameter and effective equation of state of dark energy. This study is mainly based on the Hubble parameter data from the cosmic chronometer observations. Other cosmological...
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M Laxman (IIT Madras)
Most of the gravitational wave (GW) signals detected so far by LIGO and Virgo detectors consist of comparable mass binary black holes (BBHs). Another interesting source of GWs is highly eccentric intermediate mass ratio inspirals (IMRIs). GW signals from IMRI sources are expected to be highly eccentric when they enter the detection band of the space based detectors such as LISA and DECIGO....
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Ritwik Acharyya (Indian Institute of Technology Kharagpur)
We demonstrate a general relativistic approach to model dark matter halos using the Einstein cluster, with the matter stress-energy comprising collisionless particles moving on circular geodesics in all possible
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angular directions and orbital radii. Such matter, as is known, allows an anisotropic pressure profile with non-zero tangential but zero radial pressure. We use the Einasto density... -
Premachand Mahapatra (BITS PILANI , K K BIRLA GOA CAMPUS)
We study the equilibrium configurations and the radial stability of spherically symmetric relativistic Neutron Stars(NS) with a polytropic equation of state (EoS) in a modified $f (R, T )$ gravity framework by introducing a quadratic term in $T$ (where $T$ is the trace of the conserved energy-momentum tensor $T_{\mu \nu}$ of the matter-energy) for the functional form of $f(R, T)$ with $f (R, T...
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Suresh Parekh (Savitribai Phule Pune University, Pune, India - 411007)
This research paper examines the Ricci scalar R and the Gauss-Bonnet invariant G to characterize a cosmological model in flat space-time via $f(R,G)$ gravity. Our model assumes that $f(R,G)$ is an exponential function of $G$ combined with a linear combination of $R$. We scrutinize the observational limitations under a power law cosmology that relies on two parameters - $H_0$, the Hubble...
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Mr Fazlu Rahman (Indian Institute of Astrophysics Bangalore)
Accurate component separation of full-sky maps in the radio and microwave frequencies, such as the cosmic microwave background (CMB), relies on a thorough understanding of the statistical properties of the Galactic foreground emissions. These Galactic emissions include Galactic synchrotron, free-free, thermal dust emissions, Anomalous Microwave Emission (AME), etc. Extracting the morphological...
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Avinash Kumar Paladi (Indian Institute of Science)
The wideband timing technique enables the high-precision simultaneous estimation of Times of Arrival (ToAs) and Dispersion Measures (DMs) while effectively modeling frequency-dependent profile evolution. We present two novel independent methods that extend the standard wideband technique to handle simultaneous multi-band pulsar data incorporating profile evolution over a larger frequency span...
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Saraswati Devi (1.IIT Guwahati, Guwahati, Assam 2. Mangaldai College, Mangaldai, Assam)
The stability of an asymptotically flat, static, spherically symmetric naked singularity spacetime
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in the novel four-dimensional Einstein-Gauss-Bonnet (EGB) gravity has been studied. Such a naked singularity is obtained from the four-dimensional EGB black
hole for large enough values of the coupling parameter. The stability and
the response of the spacetime are studied against the... -
Amit Kumar (Indian institute of technology Guwahati)
Abstract: We study the properties of the neutrino-dominated accretion flow (NDAF) around the rotating black holes. The accretion flow of this kind involves hyper-accretion rate (${\dot m} \sim 0.001-10$ $M_\odot~{\rm s}^{-1}$) and because of this, the disk becomes geometrically as well as optically thick that makes it difficult for photons to escape. On the contrary, neutrinos easily move out...
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Mr Anjan Kar (Indian Institute of Technology Kharagpur)
A new two-parameter, static and spherically symmetric regular geometry is proposed, which, for specific parameter choices, represents a geodesically complete, regular black hole. However, unlike most regular black holes which have Schwarzschild spacetime as their singular limit, our spacetime reduces to a singular, mutated Reissner–Nordström geometry, for a particular choice of parameters. The...
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Dipankar Laya
The present work deals with a complex scalar field in scalar tensor gravity theory in the background of spatially flat Friedmann-Lema$\hat{i}$tre-Robertson-Walker (FLRW) geometry. Noether symmetry analysis has been used to determine the classical cosmological solution of a scalar field in scalar-tensor theory with the scalar field as a nonminimally coupled complex field. Noether symmetry...
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Aman Srivastava
The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years of uGMRT observations. We present the results of single-pulsar noise analysis for each of these 14 pulsars using the InPTA DR1. For this purpose, we consider white noise, achromatic red noise, dispersion measure (DM) variations, and scattering...
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Mr SHOUVIK SADHUKHAN (INDIAN INSTITUTE OF SPACE SCIENCE AND TECHNOLOGY THIRUVANANTHAPURAM)
In this work we have discussed the origin of cosmic viscosity with the in of deformed cosmic phase space geometry. We have introduced the Non-Commutative(NC) deformed geometry and shown that the transformation from non-Riemannian geometry to Riemannian geometry (From Non-Commutative to Commutative(C) geometry) can provide the dissipation in cosmology. A single scalar field in deformed...
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Sharvari Nadkarni-Ghosh (IIT Kanpur)
Recent observations have indicated that all is not well with the standard Lambda-Cold-Dark-Matter (LCDM) model of the Universe. Clues that help constrain the modifications to LCDM are hidden in the large scale structure of the Universe. The fractional density and peculiar velocity are the two main variables that are used to characterize this structure. When the perturbations are small, linear...
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Mr Ujjwal Kumar Upadhyay (Indian Institute of Science, Raman Research Institute)
While fitting a non-linear model to data, it is common to consider errors only in the dependent variable and treat other variables as perfectly measured. A more flexible model fitting considering errors in independent variables is expected to better estimate the parameters of the model from the same data. We employ a Bayesian method to consider redshift errors in the Pantheon sample of Type-Ia...
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KHURSID ALAM (Saha Institute of Nuclear Physics)
Abstract: Production of gravitationally coupled light moduli fields must be suppressed in the early universe, so that its decay products do not alter Big Bang Nucleosynthesis (BBN) predictions for light elements. On the other hand, the moduli quanta can be copiously produced non-thermally during preheating after the end of inflation. In this work, we study the production of moduli in the...
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Andrew Miller
The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. Continuous waves allow us to probe not just the canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple...
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RAJ KISHOR JOSHI (ARIES, Nainital)
We present the axisymmetric numerical simulations of the relativistic transonic jets around black holes driven by the radiation field of the accretion disk. We show that starting from a very low velocity at the base, jets can be accelerated to relativistic terminal speeds. Our results show the morphology of the jets during their different evolutionary stages. In addition to acceleration, the...
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Ganga R Nair (National Institute of Technology, Karnataka)
In Loop Quantum Cosmology (LQC), a quantum bounce precedes inflationary epoch. The presence of a quantum bounce leads to a departure from scale invariance of the spectra of primordial perturbations. Studies conducted mostly at the level of the primordial power spectrum show that this departure from scale invariance is a remnant of the bounce and is largely independent of the form of the...
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Sucheta Datta (St.Xavier's College (Autonomous), Kolkata, India)
In this paper we apply the Regge-Wheeler formalism to study the propagation of axial and polar gravitational waves in matter-filled Bianchi I universe. Assuming that the expansion scalar Θ, of the background space-time is proportional to the shear scalar σ, we solve the background field equations in the presence of matter (found to
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behave like a stiff fluid). We then derive the linearised... -
Sanjit Debnath (Aryabhatta Research Institute of Observational Sciences (ARIES), INDIA)
We investigate the time evolution of the transonic-viscous accretion flow around a non-rotating black hole. The input parameters used for the simulation are obtained from semi-analytical solutions. This code is based on the TVD routine and correctly handles the angular momentum transport due to viscosity. The thermodynamic properties of the flow are described by an equation of state with a...
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Tanmoy Chakraborty (Indian Association for the Cultivation of Science)
We attempt a computation of the spectrum of scalar particles produced in the background of a spherical gravitational wave. The idea was adopted form the great work by Parker in 1976 where he showed the phenomenon of particle creation in the background of an early expanding universe, the spectrum of which was found to be thermal. In fact, any dynamical spacetime, which is a spacetime having no...
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Mr Ayanendu Dutta (Jadavpur University, Kolkata)
In this talk, the particle motion around the naked singularity and black hole of Kerr-Newman spacetime will be discussed with a special attention on the closed timelike orbits. For KN black hole, the Cauchy surface is always located inside the inner horizon where particles with positive angular momentum that co-rotate with the spacetime can only pass through. It is found that in both the naked...
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147. Perturbing the perturbed: Quasi-normal mode instability in asymptotically de Sitter black holesSubhodeep Sarkar (Indian Institute of Information Technology, Allahabad; Centre for Theoretical Physics, Jamia Millia Islamia)
In this talk, we aim to address the question of whether the quasi-normal modes, which represent the characteristic frequencies associated with perturbed black hole spacetimes and are central to the stability of these black holes, are themselves stable. We begin by presenting a general method for transforming to a hyperboloidal coordinate system in both asymptotically flat and asymptotically de...
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Ms ASTHA KAKKAR (DEPARTMENT OF PHYSICS AND ASTROPHYSICS, UNIVERSITY OF DELHI, DELHI - 110007, INDIA)
Abstract: The primary ingredient for studying the phases of a quantum field theory is the effective action, which to the leading order involves computation of one-loop determinants. In this talk which is based on our papers [1] and [2], I will describe a method for computing one-loop partition functions for scalars and fermions on AdS$_{d+1}$ for zero and finite temperature for arbitrary...
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Avijit Chowdhury
Astrophysical Compact objects are surrounded by accretion disks. The photons emitted by the accreting compact object interacts with the plasma in the interstellar medium. In this work, we investigate the dynamics of electromagnetic field propagating in the background of Exotic Compact Objects. We discuss whether or not bound states can form in the case of exotic compact object and how the...
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Ms Banashree Baishya (IIT Guwahati)
Pole-skipping is a phenomenon when lines of poles and zeroes of retarded Green's function intersect- which means a would-be pole gets skipped in a complex $\omega-k$ plane. People have claimed these points are connected to the Lyapunov exponent and butterfly velocity of a chaotic system. In this talk, I will show the effect of scalar-Gauss-Bonnet coupling (higher curvature term coupled to the...
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Neev Shah (IISER, Pune & ICTS-TIFR, Bengaluru)
Lensing due to intervening matter such as clusters or galaxies can (de)magnify a gravitational-wave (GW) event, leading to a biased measurement of the source mass and redshift. Hierarchical inference on the detected GW events can be performed to estimate the population properties of binary black holes, such as their mass and redshift distributions. Currently, it is assumed that the current...
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Mr Chandrachud B. V. Dash (Birla Institute of Technology and Science, Pilani)
In this study, we investigate a cosmological model involving a negative cosmological constant (AdS vacua in the dark energy sector). We consider a quintessence field on top of a negative cosmological constant and study its impact on cosmological evolution and structure formation. We use the power spectrum of the redshifted HI 21 cm brightness temperature maps from the post-reionization...
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Mr Vaibhav Trivedi (Fergusson College, Pune - 411004)
In this study, The power-law solution for an isotropic and homogeneous universe under $f(R, T)$ gravity is examined by taking into account its functional form, $f (R, T) = R + \xi RT$, where $\xi$ is a positive constant. We have constructed the field equation in f(R, T) gravity for homogeneous and isotropic space-time. The solution of the constructed model is given by the $a = \alpha...
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Raj Patil (Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Humboldt University)
The observations of gravitational waves (GW) have proved to be a probe for the physics of celestial objects like black holes (BH) and neutron stars (NS). Such detections have the potential to unravel the mysteries of cosmic origins, equations of state of compact objects and will prove to be a test of the theory of general relativity. To successfully achieve these scientific goals, it is...
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Rajorshi Chandra (Raman Research Institute)
The Cosmic Microwave Background continues to be a cornerstone of precision cosmology. It has provided the most accurate parameter constraints for the widely used $\Lambda$ cosmological constant and Cold Dark Matter ($\Lambda$CDM) model, via missions like COBE, WMAP, and Planck. In precision regimes, accounting for the weak lensing of the CMB photons by the large structure gravitational...
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Priyanka Gawade (IUCAA, Pune)
Primordial black holes, which could have formed during the early Universe through overdensities in primordial density fluctuations during inflation, are potential candidates for dark matter. We explore the use of lensing parallax of Gamma ray bursts, which results in different fluxes being observed from two different vantage points, in order to probe the abundance of primordial black holes in...
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Dr Md Riajul Haque (Indian Institute of Technology Madras)
We compare the dark matter(DM) production processes and its parameters space in the background of reheating obtained from two chief systems in the early Universe: the inflaton $\phi$ and the primordial black holes (PBHs). We concentrated on the mechanism where DMs are universally produced only from the PBH decay and the generation of the standard model plasma from both inflton and PBHs....
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V. Sreenath (National Institute of Technology Karnataka, Surathkal)
Analysis of Planck data has revealed to us the presence of several anomalies in the Cosmic Microwave Background (CMB). Many investigations have revealed to us the interconnection between several such anomalies. In this talk, we highlight the primordial connection of some of these anomalies. In particular, we analyse certain templates of the primordial power spectrum and explain how features in...
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Uddeepta Deka
Gravitational lensing of gravitational waves (GW) opens up the exciting possibility of studying the properties of the lens. If the wavelength of GW is comparable to the Einstein radius of the lens, diffraction effects modulate the GW waveform. Previous work has shown that if the lens is a stellar mass Schwarzschild black hole (BH), and the GWs have wavelengths detectable by the...
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Sunil singh Bohra (Phd student)
The general theory of relativity (GR) states that black holes can possess three hairs, namely
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mass, charge, and angular momentum. Nevertheless, modifications to GR have the potential
to alter the spacetime geometry by introducing additional hairs. In light of a potential solution
to the so-called hierarchy problem in the standard model of particle physics, GR may be
modified through the... -
AVINASH TIWARI (IUCAA, PUNE)
The accelerated motion of binary black holes (BBHs) can be constrained by the corresponding gravitational waves (GWs) they emit. We investigate the prospects of detecting this acceleration in future third-generation and proposed space-based GW detectors. Since this acceleration could be indicative of the binary's formation channel, we also forecast accelerations of BBHs in dense stellar...
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Prof. Samir Mandal (Indian Institute of Space Science and Technology)
It is widely postulated that the high-energy radiation in X-ray binary systems arises from the upscattering of photons originating from the accretion disk, likely due to interactions with an electron cloud or a corona. Nevertheless, our understanding of the exact geometry and orientation of these coronal structures remains limited. In recent times, spectro-polarimetry studies have emerged as a...
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Mohammad Kamran (Uppsala University)
Observations of the neutral hydrogen (HI) 21-cm signal have the potential to map out the large-scale structures (LSS) of our Universe during the post-reionization era (z ≲ 6). Several present and future experiments are planned to give their efforts to probe the signatures of the LSS inherent in the expected signal over a large redshift range. A correct prediction of the expected signal demands...
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Souvik Jana (ICTS-TIFR)
Third generation gravitational wave (GW) detectors are expected to detect millions of binary black hole (BBH) mergers during their operation period. A small fraction of them (∼1%) will be strongly lensed by intervening galaxies and clusters, producing multiple observable copies of the GW signals. The expected number of lensed events and the distribution of the time delay between lensed images...
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Chandra Shekhar Murmu (Indian Institute of Technology Indore)
The high-redshift observations of galaxies with instruments like the JWST can be complemented with the upcoming SKA, which will map the early IGM via intensity mapping of the redshifted 21cm signal with improved sensitivity over the current generation of radio interferometers. These star-forming galaxies are expected to emit most of the bulk of ionizing photons during the Epoch of Reionization...
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GARGI SEN (Indian Institute of Technology Guwahati)
We study the relativistic, inviscid, advective accretion flow in a stationary axisymmetric Kerr-like wormhole spacetime characterized by the spin parameter ($a_{\rm k}$) and the dimensionless parameter ($\beta$). While doing this, we solve the governing equations that describe the relativistic accretion flow in a Kerr-like wormhole and calculate all types of accretion solutions, including...
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Mr Soumik Bhattacharya (Cooch Behar Panchanan Barma University, WB)
In recent years, there has been a growing interest in understanding the General Theory of Relativity (GTR) in several ways for the construction of stellar modeling. One of such modification is the inclusion of higher order curvature terms in the Lagrangian. By introducing a quadratic form of the Riemann tensor to the standard Einstein-Hilbert action Lovelock extended GTR in higher dimensions,...
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Ms Neha Sharma (International Centre for Theoretical Sciences (ICTS))
The lensing of gravitational waves occurs when it passes near massive objects like galaxies and clusters that bends its path. The detection of the first lensed gravitational wave is expected within the next few years. Decihertz detectors such as Lunar Gravitational Wave Antenna (LGWA) are expected to detect gravitational waves from intermediate mass blackhole mergers and white dwarf binaries....
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Mr Kabir Chakravarti (CEICO, FZU, Prague)
Einstein's General Relativity (GR) is perfectly utilitarian but is considered not yet complete, mainly because of the presence of singularities and its general incompatibility with a quantum description. This had historically motivated a lot of attempts at quantising gravity. The (adiabatic invariant) area quantisation hypothesis by Beckenstein and Mukhanov in 1974 was the first step towards a...
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Sanasam Surendra Singh
Using the dynamical system approach, we investigated the stability condition of two considered models in $f(T,\phi)$ gravity where $T$ is the torsion scalar of teleparallel gravity and $\phi$ is a canonical scalar field. In this context, we are concerned with the phenomenology of the class of models with non-linear coupling to gravity and exponential potential. We assume the forms of G(T) as...
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Bhargabi Saha (Research scholar)
It has been long since chaotic inflation has explained the inflationary epoch of the early Universe. Although it has explained the particle creation mechanism via parametric resonance in the reheating region, it has not been employed to study the backreaction of particle creation in the inflationary phase.
In the present work, we take the minimal model of chaotic inflation and show that...
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Mr Sree Mahesh Chandran (Indian Institute of Technology Bombay)
Understanding the emergence of classical behavior from a quantum theory is vital towards establishing the quantum origin for the temperature fluctuations observed in the Cosmic Microwave Background (CMB). This talk presents how a real-space approach can comprehensively address this problem even in the leading order of curvature perturbations. Spatial bipartitions of quantum fluctuations are...
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Alapati Tharaka Rama Chowdary (Indian Institute of Technology, Bombay)
One of the key aims of next-generation gravitational wave detectors is to test General Relativity (GR) in the strong gravity regime. It is expected that gravity is modified in the strong gravity regime. Hence, it is imperative to obtain rotating black hole solutions in modified theories of gravity, look at their quasinormal mode (QNM) signatures, and obtain the difference between the new...
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Subhajit Barman (Indian Institute of Technology Madras)
We investigate the radiative processes involving two entangled Unruh-DeWitt detectors that are moving on circular trajectories in (2+1)-dimensional Minkowski spacetime. We assume that the detectors are coupled to a massless, quantum scalar field, and calculate the transition probability rates of the detectors in the Minkowski vacuum as well as in a thermal bath. We also evaluate the transition...
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Yuvraj Sharma
The future of Gravitational Wave (GW) detectors [LVK] have made remarkable progress, with an expanding sensitivity band and the promise of exponential increase in detection rates for upcoming observing runs [O4 and beyond]. Among the diverse sources of GW signals, eccentric Binary mergers present an intriguing and computationally challenging aspect. We address the imperative need for efficient...
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Ms Madhukrishna Chakraborty (Jadavpur University)
The present work deals with the classical and quantum aspects of the Raychaudhuri equation in the framework of $f(T)$-gravity theory. In the background of homogeneous and isotropic Friedmann–Lemaitre–Robertson-Walker space-time, the Raychaudhuri equation has been formulated and used to examine the focusing theorem and convergence condition for different choices of $f(T)$. Finally in quantum...
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Dr Shibendu Gupta Choudhury (S. N. Bose National Centre for Basic Sciences)
The intrinsic angular momentum of fermions can generate torsion in spacetime. This gives rise to an effective four-fermi interaction that fermions experience within a fermionic distribution. This interaction is expected to become significant when densities start to grow. In this contribution, I will discuss some findings from our ongoing exploration regarding the role of this interaction in a...
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Purba Mukherjee (Indian Statistical Institute, Kolkata)
I shall discuss the prospects of machine learning algorithms, namely Gaussian processes and neural networks, to reconstruct the evolutionary history of the Universe with present available observational data independent of any cosmological model. Through this reconstruction, one can constrain different cosmological parameters, which can serve as a promising tool in addressing the rising...
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Mr Hrisikesh Thakur (Indian Institute of Technology, Guwahati)
Kofman, Linde and Starobinsky had showed that preheating can occur due to a huge amount of particle creation by parametric resonance after the inflationary era of the Universe. In the $\phi^2$ model, they confirmed the existence of narrow and broad resonances as well as stochastic resonance in the presence of an expanding background, by means of exact numerical computation of the corresponding...
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Mr SHOUVIK SADHUKHAN (INDIAN INSTITUTE OF SPACE SCIENCE AND TECHNOLOGY THIRUVANANTHAPURAM)
We have proposed a new phase space coordinate system for scalar field theory that can provide a detailed analysis of the cosmological evolutionary phases in a more generalized manner. We have studied \textcolor{red}{(how many)} intermediate states of cosmic inflations. We have discussed fixed point analysis for these phases. The new phase space dynamics discussed here provide a new family of...
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Pankaj Saini (Chennai Mathematical Institute)
Next generation gravitational wave (GW) detectors are expected to detect $10^4 \mbox{--} 10^5$ binary black holes (BBHs) per year. Understanding the formation pathways of these binaries is an open question. Orbital eccentricity can be used to distinguish between the formation channels of compact binaries as different formation channels are expected to yield distinct eccentricity distributions....
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Malalay Ramazanoghly, Dr Ahmad Shariati (Al-Zahra University)
We have examined data from 852 Coma cluster galaxies from three different catalogs and grouped them according to their velocity and magnitude in two fields to survey the core (Coma1) and the periphery (i.e. southwest of the core and centered on NGC4839; Coma3). We have identified a group of these galaxies that appear to be a dense cluster (main cluster) of 545 galaxies (430 in Coma1 and 115 in...
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SOMITA DHAL (BIRLA INSTITUTE OF TECHNOLOGY, MESRA, RANCHI,INDIA ,835215)
A plethora of knowledge about the universe’s chronology may be found in the spectral properties of the CMB energy spectrum. The spectral aberrations of the CMB complement all other cosmological investigations. According to the astonishing measurement of the CMB spectrum by COBE/FIRAS, the CMB spectrum resembles a blackbody with a temperature of TCMB = 2.72548 ± 0.00057 K. This paper aims to...
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Manish Kumar Sharma (Birla Institute of Technology and Science pilani, Goa Campus)
If the dark matter is a Dirac fermion($\chi$) and it has an electric and magnetic dipole moment, it can couple with the Standard Model photon through a dimension five effective operators, suppressed by a New Physics(NP) scale $\Lambda$. We probe the parameter space in terms of Dark Matter mass ($m_\chi$) and the New Physics scale $\Lambda$ via a mono-photon signal at the upcoming...
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Sreetama Das Choudhury (INDIAN INSTITUTE OF TECHNOLOGY)
We revisit the black hole X-ray binary source XTE J1859+226 during its outburst phase in 1999-2000 and carry out the spectral and timing analyses using RXTE observations. Over the course of outburst, type-B QPO is observed multiple occasions and the combined spectro-temporal results reveal enhanced hard X-ray contributions as ${\rm QPO}_{\rm rms}\% \sim 1-3$, covering fraction $\sim 0.4-0.6$...
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Kajol Paithankar (Indian Institute of Astrophysics, Bengaluru, India)
We investigate the generalised radial Rindler trajectories and their corresponding Rindler horizons in the background of the Schwarzschild spacetime. In a curved spacetime, a covariant definition for Rindler trajectories is provided in terms of the generalised Letaw-Frenet equations. A generalized Rindler trajectory remains linearly uniformly accelerated throughout its motion with constant...
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Kajol Paithankar (Indian Institute of Astrophysics, Bengaluru, India)
We demonstrate an equivalence between the Minkowski photon emission rate in the inertial frame for an accelerating charge moving on a Rindler trajectory with additional transverse drift motion and the combined Rindler photon emission and absorption rate of the same charge in the Rindler frame in the presence of the Davies-Unruh thermal bath. We further show that the equivalence can be extended...
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Atrideb Chatterjee (Inter-University Centre for Astronomy and Astrophysics)
The cold dark matter (CDM) paradigm provides a remarkably good description of the Universe’s large-scale structure. However, some discrepancies exist between its predictions and observations at very small sub-galactic scales. To address these issues, the consideration of a strong interaction between dark matter particles and dark radiation emerges as an intriguing alternative. In this talk, we...
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Mr VIBHAVASU PASUMARTI (INDIAN INSTITUTE OF TECHNOLOGY HYDERABAD)
The study aimed to examine the connection between radio pulsars and ultra-high energy neutrinos using the IceCube catalog of point source neutrino events. For this purpose we use the unbinned maximum likelihood method to search for a statistically significant excess from each of the pulsars in the ATNF catalog.
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Next, we performed a Stacked search to further *enhance signal to noise... -
Bihag Dave (Ahmedabad University)
Recently Ultra Light Dark Matter (ULDM), where DM is described by a scalar field with $m\sim 10^{-22}\ \text{eV}$ has emerged as a promising alternative to the standard Cold Dark Matter (CDM) model. However, viability of models with no self-interactions (also called Fuzzy Dark Matter), is under question as relevant masses are increasingly constrained using various astrophysical and...
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subhadip sau (Jhargram Raj College)
The existence of black holes is one of the most astonishing predictions of general theory of relativity. The Event Horizon Telescope (EHT) collaboration's latest observations, as well as the discovery of gravitational wave signals by the Laser-Interferometer Gravitational Wave-Observatory (LIGO) and Virgo corroborate the existence of these celestial objects. Despite the success, there are...
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gowtham sidharth (Vellore Institute of Technology)
In this paper, We have studied the Shadow cast by a rotating Bardeen
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black hole in the background of asymptotically safe gravity. Using Hamilton-
Jacobi variable separation method we have derived the null geodesics and the
shadow observables. We have found that the size of the shadow decreases with
an increase in ASG parameter (ω) and gets more distorted with an increase
in spin parameter... -
Mr DILIP KUMAR (PhD research scholar)
There are several observed Gamma Ray flares which are of short duration which cannot be explained by the conventional models of black holes, active galactic nuclei and neutron stars. Some of these also correspond to high redshift values. The nature of the bursts indicate an extremely compact emission region typically associated with magnetic reconnections. We conjecture that these magnetic...
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Tanima Duary (INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH KOLKATA)
Under the assumption of thermal equilibrium between the horizon and the fluid inside, we conducted a thermodynamic stability analysis on a model designed to mimic the characteristics of the $\Lambda$CDM model, which is the prevailing framework for portraying the cosmic acceleration. The scale factor for this model is defined as $a\sim \sinh^{2/3}(t/t_0)$. The Hayward-Kodama temperature is...
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Sasmita Kumari Pradhan (PhD Scholar, Sambalpur University)
In this work, we present singular bounce scenario
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in the framework of the generalised Brans-Dicke (GBD)theory where an evolving BD parameter along with a self-interacting potential is considered. The GBD field equations are derived for an anisotropic space time to provide a more general approach to the cosmic expansion. The evolutionary behaviour of the Brans-Dicke scalar field, dynamical... -
Bikash Chandra Paul (North Bengal University)
We present flat emergent universe with a dynamical wormhole with a modified matter described by nonlinear Equation of state (nEoS) in Einstein’s gravity. The Emergent universe (EU) is free from initial singularity accommodating late accelerating universe satisfactorily. The basic assumption of the original EU model is that the present universe emerged out from an initial Einstein static...
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Ms O. P. Jyothilakshmi (Department of Sciences, Amrita School of Physical Sciences, Coimbatore, Amrita Vishwa Vidyapeetham, India)
We obtain the global properties of static and slowly rotating self-gravitating Bose-Einstein condensate (BEC) stars and study the effect of temperature on the stellar structural properties. For this we consider a recently developed temperature dependent equation of state of BEC stars formed due to Cooper pairing of nucleons. We use the Hartle-Thorne slow rotation approximation equations to...
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Mr Divyesh Solanki (Indian Institute of Information Technology Allahabad)
We study the finite temperature effects on the soft graviton theorem and the gravitational memory effect using the thermofield dynamics formalism. The soft factor depends on the nature of the scatterers at finite temperatures. Thus, the universal behaviour of the soft factor is lost. However, the universality in the scattering cross-section of the soft processes is observed at low...
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Dr Suman Ghosh (Birla Institute of Technology Mesra)
Recently we have shown that Ellis-Bronnikov wormholes embedded in warped background do satisfy energy conditions. We present analysis of particle trajectories, geodesic congruences in such wormhole spacetimes and their quasinormal modes. We emphasize on distingushing signatures of the wormhole geometry and the warped extra dimension.
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Mr Suvikranth Gera (BITS PILANI KK BIRLA GOA CAMPUS)
In this study, we analyse the quasinormal modes of black holes occurring within the framework of degenerate gravity. We investigate the properties of the asymptotically flat spacetimes introduced recently in [JCAP 02(2022)02] which are solutions to the degenerate Einstein Gauss-Bonnet(dEGB) action and belong to a much larger class of solutions which include cosmological constant. These...
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Dr Biplob Sarkar (Department of Applied Sciences, School of Engineering, Tezpur University)
We report the analysis of the Z-track neutron star (NS) low-mass X-ray binary (LMXB) GX 17+2 using the simultaneous data from the AstroSat (LAXPC/SXT) and NICER mission data. On segmenting the hardness intensity diagram (HID) into three slices—horizontal branch (HB), hard apex (HA), and normal branch (NB)- we investigate the variability of the source and its spectral state evolution throughout...
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Subhankar Patra
The study of accretion flow for astrophysical sources like active galactic nuclei (AGNs), black hole X-ray binaries (BHXRBs), etc., is essential to understand their spectral features. Nowadays, theorists hugely focused on the alternative gravity theory to explain some distinctive observational results from the usual Kerr BH. One such emerging non-Kerr spacetime is the Johannsen-Psaltis (JP)...
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Haridev S R
The phenomenon of spontaneous symmetry breaking (SSB) is one of the cornerstone paradigms of modern physics. In this work, we address fundamental questions related to the role of observers and curvature in phase transitions associated with SSB. Our study involves scalar field theory with $\lambda\phi^{4}$ interaction and the linear sigma model (LSM) at leading order in $1/N$. Employing these...
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Ayan Chakraborty (INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI)
The phenomena of Squeezing and chaos have recently been studied in the context of inflation. We apply this formalism in the post-inflationary preheating phase. During this phase, inflaton field undergoes quasi-periodic oscillation, which acts as a driving force for the resonant growth of quantum fluctuation or particle production. Furthermore, the quantum state of the fluctuations is known to...
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Jose Mathew (The Cochin College)
In this paper, we discuss a general method to obtain exact cosmological solutions in modified gravity, to demonstrate the method it is employed to obtain exact cosmological solutions in f(R,phi) gravity. Here, we show that, given a particular evolution of the Universe, we could obtain different models of gravity that give that evolution, using the same construction. Further, we obtain an exact...
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Dipanshu G (IISER Pune & RRI)
Observations of the cosmic microwave background (CMB) anisotropies have played a key role in developing modern cosmology. Detailed and accurate measurements of the CMB anisotropies tell us a lot about the global properties, the constituents, and the history of the universe. Standard cosmological model assumes Statistical Isotropy and Gaussianity of the CMB anisotropy in FRW cosmology. There...
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Dr Seema Satin (Indian Institute of Science Education and Research Kolkata)
I will present a new upcoming theme of research based on stochastic aspects of the cosmic fluids. The aim is to develop new foundations for a mesoscopic intermediate scale theory, which helps to probe nature and evolution of dense matter in compact stars and early universe cosmology around the era of decoherence of the inflaton field, at intermediate sub-hydro scales. Connections of...
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Dr Sini R (Providence Women's College,Calicut)
We investigate the affine perturbation series of the deflection angle of a ray near the photon sphere of by kazakov-solodukhin black hole . The values of strong field parameters calculated and analyzed its variation with deformation parameter. With the help of lens equation the expression for angular position of innermost image, the angular separation of outermost image with the remaining...
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Pranjal Sarmah (Dibrugarh University)
Some observational deviations from the standard cosmological principles of isotropy and homogeneity lead to create more interest among the researchers on studying anisotropic characteristics of the Universe in recent times. In this context the locally rotationally symmetric Bianchi type I (LRS-BI) metric is appeared to be suitable and simplest candidate for studying anisotropic nature of the...
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Dr Priyanka Sarmah (National Tsing Hua University, Taiwan)
Superradiance in spinning black holes is an intriguing phenomenon through which the black hole loses its energy and angular momentum over time. In this work, we explore the transient effect of the superradiance process in active galactic nuclei (AGN). We aim to see the spin-down effect on the accretion disk using an analytic model named Shakura Sunayev. Considering this model, we show how...
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Mr Rajesh Karmakar (Indian Institute Of Technology, Guwahati)
Within the framework of static-charged and rotating black hole spacetime, an extensive amount of work suggests that the bosonic fields exhibit superradiant scattering. In this work, we have investigated the scattering of scalar waves and electromagnetic (EM) waves for Schwarzschild black hole in the ring down phase (we refer to this black hole as the ``ringing black hole"), which is the last...
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Akash Maurya (International Centre for Theoretical Sciences, Bangalore)
Orbital eccentricity of coalescing compact binaries produces a strong imprint in the gravitational waves (GWs) emitted by these systems. Its presence indicates at dynamically assembled binaries in dense stellar environments like globular clusters, nuclear star clusters, etc. Hence, detecting an eccentric merger will significantly enhance our knowledge about the formation channels of these...
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Soumen Nayak
Magnetic fields can be generated in cosmic string wakes due to the Biermann mechanism in the presence of neutrino inhomogeneities. As the cosmic string moves through the plasma, the small magnetic field is amplified by the turbulence in the plasma. Relativistic charged particles that cross the magnetized wake of a cosmic string will therefore emit synchrotron radiation. The opening angle of...
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Sudip Naskar
In Loop Quantum Cosmology
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(LQC), inflation is preceded by a bounce. The scalar and tensor power
spectra and scalar bispectrum have been investigated in LQC. These
studies show that the presence of the bounce sets a new scale in the
problem. The spectra of perturbations with wavelengths comparable to or
larger than this scale departs from the nearly-scale invariant behaviour
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Kaustav Das (Indian Association for the Cultivation of Science)
A remote observer in black hole spacetime sees the creation of a pair of particles. Now, one can use Bell’s operator to test whether the two spacelike-separated particles (one outside the horizon and one inside the horizon) are quantum mechanically entangled or not. Also, we describe a prescription to check entanglement of particles created outside the horizon and inside the horizon using...
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Mr Debojit Paul (Department of Physics, Gauhati University)
The presence of compact stellar orbits near the Galactic Center (GC) black hole presents a magnificent opportunity for testing modified theories of gravity as the gravitational potential ($GM/c^2r$) is equal to or more than 100 times the one encountered in the solar system. In this work, we study the effect of f(R) gravity near the GC black hole using both model dependent and independent...
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Sajad Ahmad Bhat (IUCAA)
The parametrized post-Newtonian (PN) test of general relativity (GR) currently assumes binary black holes (BBHs) in quasi-circular orbits. However, population simulations predict that a subpopulation of BBHs retain residual eccentricity in the frequency-band of ground-based detectors. To perform robust parametrized tests of GR with eccentric binaries, corrections due to orbital eccentricity...
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Parthapratim Mahapatra (Chennai Mathematical Institute, LIGO-India Scientific Collaboration (LISC))
Asymmetric emission of gravitational waves during a compact binary coalescence results in the loss of linear momentum and a corresponding `kick' or recoil on the binary's center of mass. This leads to a direction-dependent Doppler shift of the ringdown gravitational waveform. We quantify the measurability of the kick imparted to the remnant black hole in a binary black hole merger. Future...
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Dr Poulami Dutta Roy (Chennai Mathematical Institute)
Gravitational-wave observations are unique means to test general relativity (GR) in the strong-field regime. Parametrized tests of post-Newtonian theory have been very efficient in testing GR in the inspiral phase of compact binary dynamics. In this test, one introduces deformation coefficients at each post-Newtonian order in the inspiral phase of the gravitational wave which by definition are...
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Mr Masroor Sofi (Indian Institute of Astrophysics)
In this project we focus on testing statistical isotropy and Gaussianity of CMB lensing convergence maps using recently released data of the cosmic microwave background (CMB) radiation from the Atacama Cosmology Telescope
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(ACT). The CMB photons are lensed by gravitational potential wells of the
large-scale matter distribution. This CMB temperature data is converted to convergence map by... -
Dr Joseph P J (IISER Mohali)
Observation of Blackhole shadows by the VLBI Telescopes provides an excellent opportunity to test General Relativity in the strong field regime. One can use these observations to test the fundamental foundations of GR, such as Einstein's equivalence principle. In simple terms, Einstein's equivalence principle refers to simply changing the partial to covariant derivatives of the matter fields....
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Mr Samarjit Chakraborty (St. Xavier's College (Autonomous), Kolkata)
We investigate the status of the gravitational arrow in the case of spherical collapse of a fluid which conducts heat and radiates energy. In particular, we examine the results obtained by W. B. Bonnor in his 1985 paper, where he found that the gravitational arrow was opposite to the thermodynamic arrow. The measure of gravitational epoch function used by Bonnor was given by the ratio of the...
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Divyajyoti . (Indian Institute of Technology Madras)
We investigate the prospect of performing binary black hole (BBH) nature tests using spin-induced multipole moment (SIQM) measurements when the binary is fully precessing. As SIQM is strongly degenerate with spin parameters, we are interested in the degeneracies the SIQM parameter has with spin precession. We extend the previous SIQM-based BBH nature tests by incorporating two-parameter...
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Neev Shah (IISER, Pune)
Dark matter halos can enter a phase of gravothermal core--collapse in the presence of self-interactions. This phase that follows a core--expansion phase is thought to be subdominant due to the long time-scales involved. However, it has been shown that the collapse can be accelerated in tidal environments particularly for halos that are centrally concentrated. Cosmological simulations in ΛCDM...
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Dr P.C Lalremruati (Indian Institute of Science Education and Research Kolkata (IISER-Kol))
The Galactic Center supermassive black hole, Sgr A* provides an ideal laboratory for testing general relativity (GR) and constraining its alternatives. In this work, we search for GR breaking points by estimating the pericenter shift of stellar orbits having a semimajor axis in the range of (45 - 1000)au. We work with theoretical scalaron field amplitude and coupling. The scalaron mass is...
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Dr Mahavir Sharma (IIT Bhilai)
Masses of supermassive black holes (SMBH) are known to correlate with the spheroidal component of their host galaxies according to the so-called M-sigma (Magorrian) relation. A further proposal of a correlation between the SMBH mass and halo mass is a focus of research. In this talk, we propose a mechanism for the co-evolution of black holes and their host dark matter haloes based on the...
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Dr Dibya Chakraborty (Ashoka University)
In this talk, I will discuss various string-loop, warping, and curvature corrections, which are expected to appear in type IIB moduli stabilization scenarios. It has recently been a topic of active debate whether these corrections can be consistently as well as simultaneously ignored for concrete de Sitter constructions. We study this question in the presence of a new weakly-warped LVS de...
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Mr Ayanendu Dutta (Jadavpur University, Kolkata)
In my talk, I will explore the intriguing aspects of ghost-free dRGT massive gravity, which introduces two additional characteristics scales, $\gamma$ and $\Lambda$, representing non-zero graviton masses. I will delve into how these parameters influence wormhole solutions, ultimately leading to a loss of asymptotic flatness near the throat region. This inconsistency arises from the induced...
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Jyotijwal Debnath
We devise a full general relativistic formalism to study the delays caused by the light bending effect in the signal of a radio pulsar in a binary. This delay is non negligible for neutron star - neutron star binaries and even stronger for neutron star - black hole binaries. We calculate bending delays for hypothetical neutron star - black hole binaries. The values of the bending delays...
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Ritik Sharma
Almost every galaxy hosts a supermassive black hole at its center, and the mass of the black hole is correlated with the velocity dispersion of the galaxy, pointing to a co-evolution that has been a focus of research. Interestingly, supermassive black holes are detected even at redshifts greater than 6 when the Universe was very young and it is a mystery how a black hole could have grown to...
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Susobhan Mandal (IIT Bombay)
The Cold Dark Matter (CDM) hypothesis accurately predicts structure formation on cosmological scales and fits the temperature fluctuations of the Cosmic microwave background (CMB) and large-scale structure. However, observations that probe the innermost regions of dark matter halos and the properties of dwarf galaxy satellites have persistently challenged CDM. In contrast, the Modified...
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Mr PRADOSH KESHAV MV (Christ University)
The dominance of dark energy in the universe has necessitated ways to introduce a repulsive gravity source to make $q$ negative. The models for the dark energy range from $\Lambda$-CDM, K-essence, Chaplygin gas, etc. We look at the possibility where the interaction parameter $\Gamma$ plays a vital role in various cosmological models, particularly those involving interactions between dark...
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VARENYA UPADHYAYA (Indian Institute of Technology, Hyderabad)
Pulsars are fast spinning neutron stars that lose their rotational energy via various processes such as gravitational and magnetic radiation, particle acceleration and mass loss processes. This dissipation can be quantified by a spin-down equation that measures the rate of change of the frequency as a function of the rotational frequency itself. We explore the pulsar spin-down and consider the...
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Dr Vesselin Gueorguiev (Institute for Adv. Physical Studies, Sofia, Bulgaria and Ronin Institute, NJ, USA)
The talk will present a summery of the main results within the Scale Invariant Vacuum (SIV) paradigm as related to the Weyl Integrable Geometry (WIG) as an extension to the standard Einstein General Relativity (EGR). After a short sketch of the mathematical framework, the main results until 2023 [1] will be highlighted in relation to: the inflation within the SIV [2], the growth of the density...
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Dr Shyam Das (Malda college)
Compact stars are unique laboratory for studying and testing extreme conditions in terms of density and gravity. In this paper under the framework of General Relativity we have developed a theoretical model representing compact stellar objects. For this we follow the Herrera's vanishing complexity condition in addition of assuming a particular geometry corresponding to g_rr component. All...
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235. Thermalised dark radiation in the presence of PBH: Neff and gravitational waves complementarityNayan Das (Indian Institute of Technology, Guwahati)
We study the possibility of detecting dark radiation (DR) produced by a combination of interactions with the thermal bath and ultra-light primordial black hole (PBH) evaporation in the early universe. We show that the detection prospects via cosmic microwave background (CMB) measurements of the effective relativistic degrees of freedom ${\rm \Delta N_{eff}}$ get enhanced in some part of the...
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Ronit Karmakar (Dibrugarh University)
Bumblebee gravity theory is a class of vector-tensor theory of gravity with growing interest in literature. We explore a Schwarzschild-type metric corrected by Generalized Uncertainty Principle (GUP) and possessing topological defects within the framework of Bumblebee Gravity. We investigate the thermodynamic quantities associated with the black hole metric, like temperature, entropy and heat...
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Chiranjeeb Singha
There exist several well-established procedures for computing thermodynamics for a single horizon spacetime. However, for a spacetime with multi-horizon, the thermodynamics is not very clear. It is not fully understood whether there exists a global temperature for the multi-horizon spacetime or not. Here we show that a global temperature can exist for Schwarzschild-de Sitter spacetime,...
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Vaishak Prasad (International Centre for Theoretical Sciences - Tata Institute of Fundamental Research)
It is widely believed that in the post-Newtonian approach, the asymptotic gravitational fields of non-spinning black holes do not deform under the influence of its companion. Would their horizons deform? In this talk, we present an alternate approach to the problem of tidal deformations of black holes in binary mergers using the source multipole moments of their dynamical horizons and...
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SUPROVO GHOSH
The cores of neutron stars (NS) reach densities several times the nuclear saturation density and could contain strangeness containing exotic particles such as hyperons. During the binary inspiral, viscous processes inside the NS matter can damp out the tidal energy induced by the companion and convert this to thermal energy to heat up the star. In this work, we demonstrate that the bulk...
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Naba Jyoti Gogoi (PhD Research Scholar)
Topology of thermodynamics in R-charged black holes
Naba Jyoti Gogoi, Prabwal Jyoti Phukon
Dibrugarh University, Dibrugarh, India, 786004Abstract
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In this presentation, our investigation focuses on the topological aspects of thermodynamics in R-charged black holes across four, five, and seven dimensions. Specifically, the 4D R-charged black hole features four charges, while the... -
Yashi Tiwari (Indian Institute of Science, Bangalore, India)
The Hubble tension refers to the discrepancy in the value of the Hubble constant $H_0$ inferred from the cosmic microwave background observations, assuming the $\Lambda$CDM model of the universe, and that from the distance ladder and other direct measurements. In order to alleviate this tension, we construct a plausible dark energy scenario, within the framework of Horndeski gravity which is...
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Rikpratik Sengupta (Aliah University)
In this paper we have explored the possibility of constructing a traversable wormhole on the Shtanov-Sahni braneworld with a timelike extra dimension. We find that the Weyl curvature singularity at the throat of the wormhole can be removed with physical matter satisfying the NEC ρ + p ≥ 0, even in the absence of any effective Λ-term or any type of charge source on the brane. (The NEC is...
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Sunil singh Bohra (Phd student)
The ghost-free bi-metric gravity theory is a viable theory of gravity that explores the interaction
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between a massless and a massive graviton and can be described in terms of two dynamical metrics.
In this paper, we present an exact static, spherically symmetric vacuum solution within this the-
ory. The solution is spatially Schwarzschild-de Sitter, with the value of the cosmological... -
Indrajit Saha (IIT Guwahati, India)
We study ultra-light Primordial Black hole (PBH) formation from first-order phase transition (FOPT) by considering bubble collisions and false vacuum collapse as the leading mechanisms. While FOPT leads to the generation of gravitational wave (GW) spectrum with typical blue and red-tilted spectrum around a peak frequency, the ultra-light PBH, if dominates the universe for a finite epoch, can...
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Nilanjandev Bhaumik (Indian Institute of Science, Bengaluru)
Ultra-low mass primordial black holes (PBHs), which evaporate far before Big Bang Nucleosynthesis (BBN), are unconstrained to dominate the energy density of our universe for a short duration. We analyze the stochastic gravitational wave background (SGWB) signals from the domination of ultra-low mass PBHs to explain this recent discovery of SGWB from Pulsar Timing Array collaborations at...
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Ms Tabasum Rahnuma (Indian Institute of Science Education and Research, Bhopal)
The Infrared (IR) triangle, famously portrayed by Strominger, highlights the unity between soft theorems, infinite-dimensional asymptotic symmetries, and Memory Effects within a single framework. In the realm of Gravity, this is known as BMS symmetry, with a corner relating to measurable classical Gravitational Memory Effects. The revolutionary detection of gravitational waves sets the stage...
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Mr Prantik Sarmah (Indian Institute of Technology Guwahati)
Ultra-high energy cosmic rays (UHECRs) beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off provide us with a unique opportunity to understand the universe at extreme energies. Secondary GZK photons and GZK neutrinos associated with the same interaction are indeed interconnected and render access to multi-messenger analysis of UHECRs. The GZK photon flux is heavily attenuated due to the...
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Sayantan Ghosh (Indian Institute of Technology Bombay)
Intermediate-mass black holes (IMBHs) are considered to be seeds of supermassive black holes (SMBHs). Knowledge of the formation and the growth of IMBHs can lead to a better understanding of SMBH formation and galaxy evolution. In recent years, gravitational waves (GWs) have opened a new window to observe and study IMBHs. The advanced ground-based GW detectors, such as Advanced LIGO and...
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Anuj Mishra
Microlensing and eccentricity are two distinct physical effects that have not yet been observed in real gravitational wave events. While the rate of microlensed signals remains uncertain, the impact of non-zero eccentricity becomes increasingly significant as we explore the early stages of binary evolution or improve the sensitivity of detectors. Therefore, it is crucial to investigate whether...
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Jaffino Stargen D
The Unruh effect states that the transition rates of a uniformly accelerated atom in the inertial vacuum has a thermal character at a temperature proportional to the atom's acceleration. Numerous proposals, studying different system properties under varied settings, to detect the Unruh effect still await fruition as the signal of interest is very weak. Here, we make case for a suitably...
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Hari K (Indian Institute of Technology, Madras)
The two-level particle detector models, such as Unruh-DeWitt detectors(UDD), play a significant role in understanding quantum effects in different frames of reference such as the Unruh effect. These two-level quantum probes are used to study quantum field theory for different observers in flat spacetime as well as in curved spacetime. In recent years, there has been an interest in relativistic...
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subhadip sau (Jhargram Raj College)
Axions are hypothetical pseudoscalar, originally proposed as a resolution to the strong CP problem in quantum chromodynamics. These particles are considered to be potential candidate for dark matter. Hence probing axions and determining its mass is of great interest, especially near supermassive black holes like M87$*$. We have examined the phenomenon of photon axion conversion occuring in the...
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Mr ABHIJIT TALUKDAR (Gauhati University)
Big Bang Nucleosynthesis (BBN) is a strong probe for testing new physics of the early universe. Introducing modified gravity in the very early universe gives rise to some interesting effects. In this work, the effects of $f(R)$ gravity scalarons introduced in Kalita (2018, 2020, 2021) on the BBN era is investigated. Observed BBN constraints on the shift of freezeout temperature and elemental...
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Mr Bhaskar Shukla
We investigate the conjectured relationship between Lyapunov exponents and black hole phase transitions. Our study involves the computation of Lyapunov exponents for both massless and massive particles as a function of temperature. We observe that a first-order phase transition occurs at specific parameter values, where the Lyapunov exponents exhibit a discontinuity, serving as the order...
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Ms Esha Bhatia (Indian Institute of Technology Guwahati)
The line of sight velocity dispersion of the ultra-diffuse galaxies (UDGs) NGC1052-DF2 and NGC1052-DF4 have been reasonably explained only with the baryonic matter, without requiring any dark matter contribution.
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The comparable ratio between the baryonic and halo mass also ascertain the above claim for the two dark matter deficit galaxies. This paves the way for analyzing alternative gravity... -
Dr Surajit Kalita (University of Cape Town)
This abstract is primarily based on ApJ 949 (2023) 62. Understanding various physical mechanisms requires an understanding of fundamental constants, however, measurements of these constants are subject to error due to experimental constraints. Researchers have proposed several bounds on fundamental constants based on a variety of experiments and observations. These constraints are different...
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Kaushik Paul (Indian Institute of Technology Madras)
The network of LIGO-Virgo detectors has detected nearly 100 compact binary mergers in their three observing runs, among which most of the merger events are from quasicircular orbits. Though binaries tend to circularize when they enter the LIGO band, binaries formed via dynamical interactions in dense stellar clusters or through Kozai-Lidov processes can have large residual eccentricities. As...
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