General Relativity and Quantum Cosmology
We investigate gravitational lensing in Kerr spacetime in the presence of a modified photon propagation law arising from higher-curvature effective field theory corrections. Adopting a deformed dispersion relation, we analytically derive…
We investigate potential singularities in isotropic cosmological models featuring a time-varying speed of light and the gravitational constant. The governing field equations generally simplify into two-dimensional systems, subject to…
During the gravitational collapse of a massive star into a regular black hole, a new form of matter must be produced in order to prevent the formation of a central singularity. Since such matter is not present in the initial stellar…
A direct separation of the linearized Einstein equations in Kerr is presented. The trace of the perturbed metric is found to obey the spin-0 perturbation equation and so is irrelevant for the spin-2 perturbations. By combining the traceless…
Gravitational-wave (GW) observations of compact binary mergers enable precision tests of general relativity (GR) in the strong-field regime, but their reliability depends on accurate waveform modeling. Unmodeled physical effects can induce…
In Jordan-frame scalar--tensor gravity, a timelike scalar gradient defines an effective thermodynamic medium. We show that a transverse--traceless perturbation of a homogeneous shear-free background activates the local shear-work channel…
The process of Hawking evaporation, shadows and thermal fluctuations are investigated within the fabric of f(R) AdS Black Hole (BH). Specifically, the Hawking evaporation process is analyzed numerically using the Stefan-Boltzmann law. The…
In Friedmann cosmology with Einstein--Cartan torsion, the homogeneous torsion mode compatible with a separately conserved matter sector scales as $\Phi\propto a^{-3}$ and enters the Friedmann constraint as a stiff component of negative…
We examine $f(R,T)=R+\lambda T^\epsilon$ gravity models by finding the best fit parameters for various values of $\epsilon$. This is accomplished by analyzing data from the cosmic microwave background, baryon acoustic oscillation…
We formulate and numerically solve the real-frequency scattering problem for a neutral, minimally coupled, massless scalar on the rotating Kerr--Bertotti--Robinson (Kerr--BR) black-hole geometry, using a specified transparent boundary…
Using the $C-$metric in the context of $F(R)$ gravity coupled with the ModMax nonlinear electromagnetic field (the $F(R)-$ModMax theory), we derive an exact black hole solution in a four-dimensional spacetime. We then examine how various…
The interplay of Hoyle-Narlikar (HN) creation field cosmology and scalar field models for the dark sector, including the generalized Chaplygin Gas (GCG), is investigated . Though originating from distinct theoretical frameworks, both the…
We investigate the impact of spontaneous Lorentz symmetry breaking on scalar wave propagation, null geodesics, and thermodynamic behavior of four-dimensional asymptotically AdS black holes in bumblebee gravity. The static, spherically…
We study the gravitational interaction of very strong pulses of electromagnetic radiation, up to and beyond gravitational collapse. We demonstrate the existence of very compact states close to the threshold of collapse, both for a single…
We investigate the behavior of Einstein crystals in noncommutative backgrounds described by the Snyder and Snyder-de Sitter models. Possible novel effects, which may arise in realistic systems such as diamond crystals, are analyzed within a…
We study quasinormal modes (QNMs) of a minimally coupled massless scalar field on four-dimensional Schwarzschild--anti-de Sitter black holes using a Chebyshev spectral method. After compactifying the exterior domain, the radial problem is…
We develop a comprehensive relativistic framework for geometrically thin, optically thick Shakura--Sunyaev $\alpha$-viscous accretion disks around rotating Hayward regular black holes embedded in a quintessence dark energy (DE) field. The…
We study accretion and neutrino-sensitive thermal signatures of a static black hole reconstructed from a three-parameter generalized entropy. The construction is thermodynamic by design: the entropy deformation is not mapped to a…
Hamiltonian analysis of the first-order Katanaev-Volovich model of two-dimensional gravity with torsion. The first-order action already singles out natural canonical pairs: the auxiliary Lorentz scalars are conjugate to the spatial…
We study a class of Schwarzschild black holes embedded in an exponential-spheroidal dark matter halo, modelled by a phenomenological density profile $\rho(r)=\rho_0 e^{-r/r_0}$. By solving the Einstein equations for a static, spherically…