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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
In this paper, we analyze the causal aspects of evolving marginally trapped surfaces in a D dimensional
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...
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...
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...
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...
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.
The cosmological evolution equations are derived by including the scale
dependence of Newton’s constant G and cosmological constant Λ. We...
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...
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...
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...
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...
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...
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...
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...
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...
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...
A dynamical theory of gravity based on an extra dimension of vanishing
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...
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...
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...
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...
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...
We consider gravitational collapse of a fluid sphere with torsion generated by spin, which forms a black hole.
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...
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...
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...
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
the presence of a GW pulse. The resulting evolution of the geodesic separation shows the presence of...
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...
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...
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...
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...
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...
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...
The Galactic Center (GC) hosting a supermassive black hole, Sgr A* is
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....
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...
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...
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...
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...
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...
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...
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,...
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...
The stability of an asymptotically flat, static, spherically symmetric naked singularity spacetime
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...
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...
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
behave like a stiff fluid). We then derive the linearised...
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...
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...
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...
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...
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...
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...
The general theory of relativity (GR) states that black holes can possess three hairs, namely
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
In this paper, We have studied the Shadow cast by a rotating Bardeen
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...
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...
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...
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.
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
Topology of thermodynamics in R-charged black holes
Naba Jyoti Gogoi, Prabwal Jyoti Phukon
Dibrugarh University, Dibrugarh, India, 786004
Abstract
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...
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...
The ghost-free bi-metric gravity theory is a viable theory of gravity that explores the interaction
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...
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...
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...
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...
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...
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...
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.
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...
