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Francisco Lobo (University of Lisbon)15/09/2026, 10:00
Traversable wormholes provide a rigorous laboratory for probing the interplay of geometry, matter, stability, and causality in general relativity. This talk centers on the thin-shell formalism: cut-and-paste construction via the Israel-Lanczos junction conditions, precise localization and quantification of exotic matter, and stability analysis. We then examine the geometric characterization of...
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Taoufik OUALI (Mohammed First University)15/09/2026, 10:30
We review the Little Sibling of the Big Rip (LSBR) model, by introducing a new parameterization designed to alleviate its negative energy behavior at early times. The main objective of this parameterization is to improve the theoretical and observational viability of the LSBR model and provide an alternative to the ΛCDM model. The proposed parameterization is constrained using cosmic microwave...
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Maxim Khlopov (Virtual Institute of Astroparticle physics)15/09/2026, 11:00
The modern Standard cosmological scenario involves inflation, baryosynthesis and dark matter/energy. Physics of all these elements of the cosmological paradigm lays Beyond the Standard model (BSM) of elementary particles and involves in its turn cosmological probes for its study. To specify this physics the idea of multi-messenger probes of new physics is proposed, involving the set of...
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Ignatios Antoniadis (LPTHE - CNRS, Sorbonne University and AEC University of Bern)15/09/2026, 12:00
I will present a supergravity action whose bosonic part contains the f(R) gravity. In a perturbative expansion in powers of $R$, one obtains a small deformation of the Starobinsky cosmological model that solves the problem of initial conditions within the validity of the effective field theory, below the scale of tower of states predicted by the swampland distance conjecture. Moreover, it...
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Tiberiu Harko (Babes-Bolyai University)15/09/2026, 12:30
We discuss exact and numerical black hole solutions obtained in the linear representation of the conformally invariant Weyl quadratic gravity. After adopting a static spherically symmetric geometry, the vacuum field equations for the gravitational, scalar, and Weyl fields can be reformulated in a dimensionless form, which can generally be solved numerically. We detect the formation of a...
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Lehel Csillag (UBB, UniTBV)15/09/2026, 13:00
The Einstein field equations are known to follow from a variational principle based on the Einstein-Hilbert action. In this work, we investigate actions formulated in non-Riemannian geometry that produce the metric dynamics of general relativity. We classify these actions into two broad categories: (i) those whose equivalence with general relativity holds only \textit{on-shell}, and (ii) those...
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Shidong Liang (Sun Yat-sen University)15/09/2026, 15:00
We explore the interplay among noncommutativity, noncanonicality, and observability
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in quantum mechanics based on an extended Heisenberg algebra. Using the Bopp
shift technique, we develop a unified framework in which noncommutative and
noncanonical effects are systematically incorporated into quantum operators. The
resulting framework leads to modified Schrödinger, Klein–Gordon, Dirac,... -
Otto Kong (National Central University, Taiwan)15/09/2026, 15:30
A simple picture of quantum spacetime is presented for quantum physics based on the original spirit of Heisenberg and Dirac and the modern perspective of noncommutative geometry. The quantum dynamics of a particle, with or without spin, in curved spacetime is analyzed from the Heisenberg picture, based on a covariant Hamiltonian formulation. For the spin-zero particle, quantum equations of...
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Marius Oancea (University of Vienna)15/09/2026, 16:00
The geometric properties of quantum states are crucial for understanding many physical phenomena in quantum mechanics, condensed matter physics, and optics. The central object describing these properties is the quantum geometric tensor, which unifies the Berry curvature and the quantum metric. I will introduce the differential-geometric framework of vector bundles to analyze the properties of...
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Matthew J. Lake (Babes-Bolyai University)15/09/2026, 16:30
In Newtonian spacetime, the canonical description of a classical $N$-particle system requires $3N$ degrees of freedom.
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Not all of these are physical, however, since the conservation of the net momentum implies that only $3(N-1)$ accelerations are independent.
Hence, three constraints can be used to eliminate the unphysical centre-of-mass variables, at the level of the Lagrangian, leaving... -
Steven Rose (University College London)15/09/2026, 17:30
J. H. Lambert(1776) first suggested that the hypothesis of the acute angle, in which the sum of the angles of a triangle is always less than two right angles, implies the existence of an absolute measure of distance, which he implicitly defined as the linear constant relating the length of the side of a quadrilateral with three right angles to the magnitude of its acute angle (the first...
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Paul Blaga ("Babeș-Bolyai" University, Cluj-Napoca, Romania)15/09/2026, 18:00
In hyperbolic triangle geometry, the three classical triangle centers (the barycenter, the circumcenter and the orthocenter) do not align: there is no hyperbolic Euler line. It turns out, however, that there are two exotic analogues of the barycenter (the pseudobarycenter) and the circumcenter (the pseudocircumcenter) that lie on the same line as the orthocenter. This is the...
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Fei Huang (Sun Yat-sen University)15/09/2026, 18:30
We define and study the statistical physics of planar Carrollian systems. While it has been shown recently that, for general dimensions, the Carroll limit of Poincaré statistical physics typically does not converge, we show that thanks to the central extensions of the Carroll algebra in the plane, and by considering systems with angular momentum, there exists a well-defined notion of planar...
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Loïc Marsot (Sun Yat-sen University)15/09/2026, 19:00
In this talk, I will present a derivation of the equations of motion for dynamical systems with angular momentum on Finsler geometries. While point-like particles without intrinsic angular momentum follow geodesics, angular momentum generally couples to spacetime curvature, causing deviations from geodesics. I will show how these equations can be derived from requiring diffeomorphism...
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Christian Boehmer (University College London)16/09/2026, 09:30
Gravitational models with non-minimal couplings involving the trace of the energy-momentum tensor have become increasingly popular. The idea of coupling the trace of the matter tensor to the geometry can be applied to various matter models, including relativistic perfect fluids. However, it is well-known that the variational formulation of perfect fluids involves some technicalities. We...
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Peter Horvathy16/09/2026, 10:00
The large-distance behaviour of a sandwich gravitational wave can be approximated by a continuous but not necessarily smooth profile, providing us with a simplified description of particle motion. Our approximate model is consistent with the Carroll symmetry. Our strategy is illustrated by the Poschl-Teller profile.
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Qiliang Zhao16/09/2026, 10:30
We investigate velocity and displacement memory in plane gravitational waves beyond the usual sandwich approximation. The central question is whether the memory observables remain meaningful when the wave profile is continuously decaying rather than compactly supported. We find that there is a critical inverse-square falloff: faster-decaying tails can preserve memory even when the outgoing...
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David Langlois (Universite Paris Cite, CNRS, Astroparticule et Cosmologie, 75013 Paris, France)16/09/2026, 11:00
This talk will present exact solutions of non-rotating black holes and neutron stars, with primary scalar hair, obtained in a subfamily of Degenerate Higher-Order Scalar-Tensor (DHOST) theories, which include and extend Horndeski theories. I will also discuss the perturbations of these black hole solutions.
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Dumitru Ghilencea (Horia Hulubei National Institute of Physics and Nuclear Engineering (RO))16/09/2026, 12:00
Weyl conformal geometry is the natural underlying geometry of (local) gauge theories of the Weyl group (of dilatations and Poincare symmetry), such as Weyl quadratic gravity (WQG) and its generalisation, Weyl-Dirac-Born-Infeld
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action (WDBI). The WDBI action is well-defined in arbitrary d dimensions with no need for a UV regulator scale/field. A series expansion of WDBI action (in... -
Vlad-Mihai Mandric (IFIN-HH Bucharest)16/09/2026, 12:30
With current advances in gravitational wave (GW) detection made by the worldwide LIGO-Virgo-KAGRA (LVK) network of detectors, ever-more sensitive tests of gravity in the strong-field regime are now possible. This enables one to test gauge theories beyond Einstein-Hilbert action, such as Weyl gauge theories of gravity. The only anomaly-free (quantum) gauge theory of a space-time symmetry beyond...
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Miguel Pinto (Institute of Astrophysics and Space Sciences, University of Lisbon)16/09/2026, 13:00
One important stage associated with the coalescence of two black holes is the ringdown phase, during which the remnant emits gravitational radiation described by black-hole perturbation theory. This gravitational radiation is characterized by quasinormal modes (QNMs) whose frequencies and damping times encode the properties of the spacetime and the underlying theory of gravity.
Notably,...
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Neil Booker (University College London)16/09/2026, 15:00
From the action formalism, the Ricci scalar $R$ in the Einstein-Hilbert action can be decomposed into a bulk term $\mathcal{G}$ and a boundary term $\mathcal{B}$. A recent modified theory of gravity is the so-called $f(\mathcal{G})$ gravity, which arises from the action after removing its boundary term $\mathcal{B}$ from the Ricci scalar $R$ while mapping the remaining bulk term $\mathcal{G}$...
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Ladghami yahya (Mohammed I University)16/09/2026, 15:30
In this work, we investigate the black hole information loss paradox and the thermodynamics of charged black holes using the island formula. We analyze the impact of the black hole's thermodynamic behavior on information recovery, focusing specifically on the calculation of the Page time. Our results demonstrate an explicit information-thermodynamics correspondence, revealing how the...
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Ahmed Errahmani16/09/2026, 16:00
n this work, we investigate the running vacuum energy model within f(Q) gravity, where the vacuum equation of state receives dynamical corrections involving (\dot{H}) and (\ddot{H}/H). We consider two models and constrain them using DESI BAO, Pantheon+, cosmic chronometer, and CMB data. Our results indicate mild deviations from (\Lambda)CDM, with Model I remaining statistically competitive,...
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Hoang Nguyen (Babes-Bolyai University)17/09/2026, 09:30
The YONSEI group [MNRAS 544 (2025) 975] recently proposed a progenitor age-bias correction to Type Ia supernovae. Applying this empirical correction, we find that the Pantheon+ and DES5Y Hubble diagrams converge toward the special Kolb point $(w, \Omega_m)=(-1/3,0)$ in the flat $w$CDM parameter space. This point yields the compact zero-parameter logarithmic luminosity-distance relation...
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Teodora Matei (Babes-Bolyai University, Cluj-Napoca)17/09/2026, 10:00
Recent tensions in cosmological data strongly suggest that the standard $\Lambda$CDM picture may be incomplete. Many attempts have been made to alleviate the famous Hubble tension, out of which Early Dark Energy models offered one of the best theoretical frameworks so far that can possibly close the gap between early and late-time observations by dynamically modifying the spacetime background...
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Junhyuk Son (Yonsei University)17/09/2026, 10:30
Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor age. However, direct and extensive age measurements of SN host galaxies reveal a significant ($5.5 \sigma$) correlation between standardized SN magnitude and progenitor age, which is expected to introduce a serious systematic bias with redshift in...
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Himanshu Chaudhary (Universitatea Babeș-Bolyai din Cluj-Napoca)17/09/2026, 11:00
The $\Lambda$CDM model has long been regarded as the standard paradigm of modern cosmology, providing an excellent description of the Universe across a wide range of observations, from the cosmic microwave background to large-scale structure and Type Ia supernovae. However, recent cosmological observations, particularly from DESI DR2, have renewed interest in possible departures from the...
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AMINE BOUALI (Mohammed First University)17/09/2026, 12:00
We investigate the cosmological implications of an extended gravitational framework based on biconnection gravity, constructed from the Schr\"odinger connection and its dual. In this approach, the difference between the two connections defines the mutual curvature, which encodes the non-Riemannian geometric degrees of freedom, while their symmetric combination reduces to the Levi-Civitae...
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Tania Flavia Ciceo (Babeș-Bolyai University, Faculty of Physics)17/09/2026, 12:30
A bare strange star carries a thin electron layer, the electrosphere, whose overcritical electric field creates electron-positron pairs through the Schwinger mechanism. We revisit two quantities studied in earlier kinetic calculations, the surface pair-creation rate and the evolution of the electric field. We also extend the study by adding relaxation-time collisions. The calculation uses an...
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Cristian Croitoru (Technical University of Cluj Napoca)17/09/2026, 13:00
Faint satellite streaks are difficult to detect in astronomical images. High sensor dynamic range, stellar clutter, and atmospheric noise can hide these weak linear features. Global normalization can remove useful information because background noise can dominate the normalized image. We explore different preprocessing stages, from adaptive normalization to methods that enhance geometric and...
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David Pereira (Institute of Astrophysics and Space Sciences; Faculty of Sciences, University of Lisbon)17/09/2026, 15:00
We develop a covariant first-order thermodynamic description of Jordan-frame tensor–multi-scalar gravity by interpreting the additional gravitational degrees of freedom as an effective imperfect fluid. Unlike the single-field case, the presence of several scalar directions introduces independent thermal channels that cannot, in general, be reduced to a single effective temperature variable. We...
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Simão Marques Nunes17/09/2026, 15:30
In this talk I will discuss cosmological tests of gravity theories, in particular I will focus on non-metric extensions. I will present two realizations within the f(Q) gravity framework: a minimal inverse non-metricity model, which introduces no additional free parameters relative to ΛCDM, and a self-accelerating logarithmic model, with a general branch (sLog) and a DGP-like limit (sDGP)....
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Anna Horvath17/09/2026, 16:00
In the Kaluza–Klein theory, one extra spatial dimension is added to usual spacetime. On one hand, particles moving in it gain excitations leading to a mass spectrum, which can be associated with hadronic states. Neutron stars are modelled using the equation of state of an extra-dimensional interacting zero-temperature Fermi gas. Macroscopic observables are calculated, compared to astronomical...
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Eissa Alnasrallah (University College London)17/09/2026, 17:00
Modified gravity models with nonminimal coupling with matter have gained interest in the recent years due to their distinctive characteristics of breaking the stress-energy tensor conservation, entailing an additional force term. When applied to relativistic perfect fluids, such models can mimic late time acceleration and provide alternatives to dark sector interactions. The modified fluid...
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Enikõ J. M. Madarassy (Department of Physics, Babes-Bolyai University, Cluj-Napoca, Romania)17/09/2026, 17:30
The zero temperature dynamics of weakly interacting boson particles of confined and dilute BECs is described by a mean-field macroscopic wave function, ψ. To study the dynamical instabilities and relaxation to the equilibrium of the system, we perform numerical simulations using the time dependent GPE.
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Inclusion of a damping term, γ into the GPE, we model the dissipative losses, which occur... -
Oem Trivedi (Department of Physics and Astronomy, Vanderbilt University, Nashville, USA)17/09/2026, 18:00
Hermiticity is usually treated in an axiomatic way in quantum mechanics, ensuring key properties of observables in a Hilbert space. In this talk I will discuss how Hermiticity may be something deeper; a symmetry law associated with the conservation of the inner product current in space-time. We will see that this symmetry breaks in the presence of gravitational fields, causal horizons, or...
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