General Relativity and Quantum Cosmology
We investigate the equivalence of the Jordan and Einstein frames of the Brans--Dicke theory before and after relational deparametrization of the constrained Hamiltonian system. Although the two conformal formulations are equivalent at the…
Planck-scale signatures of quantum gravity may emerge semiclassically not only through modifications of spacetime geometry but also through the geometry of momentum space. In this work, we develop a $(2+1)$-dimensional framework in which a…
In this study, we study static and spherically-symmetric wormhole configurations within the recently proposed class of extended symmetric teleparallel gravities characterised by the functional form $f(Q,T)=\alpha Q+\beta T+\gamma T^{2}$,…
We use the non-linearly coupled Einstein-matter field equations to prove four theorems that bound from above the dimensionless force function ${\cal F}=4\pi r^2\cdot p(r)$ in spatially regular curved spacetimes of spherically symmetric…
Several inequivalent thermodynamic formulations of spacetimes with NUT charge obey their own first laws and Smarr relations, so macroscopic consistency alone does not fix the black hole state space. We introduce a two-horizon sector…
We investigate ghost dark energy (GDE) in a cosmological framework derived from Kaniadakis entropy. By applying the first law of thermodynamics to the FRW apparent horizon, we obtain modified Friedmann equations that include a correction…
An additional term of the form $\lambda \mathbf{T} \cdot \mathbf{C} \cdot \mathbf{T}$ in the Einstein-Hilbert Lagrangian was introduced to explain the interaction between matter and pure gravitational field [H. W. Lee and A. Qadir, Motion…
We study static, spherically symmetric self-gravitating non-Abelian 't Hooft-Polyakov monopoles in Einstein-scalar-Gauss-Bonnet gravity for two classes of scalar-Gauss-Bonnet coupling functions. We demonstrate that the branch structure of…
The discovery of the accelerated expansion of the cosmos has sparked great interest in studying the nature of the mysterious force behind this effect, often called dark energy. Several theories were proposed to study the nature of dark…
Here we discuss the effect of gravitational repulsion on geodesic deviation in the Schwarzschild-de Sitter spacetime. In particular, the geodesic deviation shows different behaviour inside or outside a critical surface, which is the divider…
We ask whether a cored dark matter (DM) correction can leave a resolved caustic trace after a spinning vacuum binary is allowed to imitate it. The vacuum comparison varies lens scale, common spin, separation, mass ratio, projected spin…
In this paper, we investigate the almost $\eta$-Ricci-Yamabe soliton as a fundamental geometric regulator for a static, spherically symmetric black hole coupled to an imperfect fluid. We have shown that the scaling parameter $\omega(r)$ is…
The LIGO-Virgo-KAGRA collaboration has reported the results for searches for sub-solar mass components in compact binary coalescence during observing run O4a. No detection candidates were identified, but the most significant seven triggers…
This work investigates the optical appearance of a rotating black hole (BH) in nonlinear electrodynamics (NED) using two illumination models, namely a celestial sphere and a thin accretion disk. The BH images are constructed using a…
In general relativity and its metric-formalism extensions, the innermost stable circular orbit and the photon ring of a charged black hole contract as the charge increases. In this paper, we discover a qualitative anomaly that violates this…
We construct two exact nonlinear-electrodynamic generalizations of the Kerr-Newman-NUT-$\Lambda$ spacetime. Imposing alignment between the principal directions of the electromagnetic field and the metric tetrad reduces the Maxwell-Faraday…
We study the scalar and Dirac perturbations of quantum-corrected black holes with cosmological constant. Using two different methods (WKB and double-null characteristic integration) we compute the quasinormal modes (QNMs) of de Sitter and…
Using asteroseismology techniques, several relations have been developed that relate the quasi-normal, non-radial oscillation mode frequencies of the proto-neutron star (PNS) to the high frequency component of core collapse supernova (CCSN)…
In this work, we study Casimir wormhole solutions and investigate satisfaction of energy conditions in the framework of Einstein-Gauss-Bonnet (EGB) gravity. We firstly find traversable wormhole solutions supported by a general form for the…
We construct Vaidya-type solutions of quasitopological gravity coupled to nonlinear electrodynamics in arbitrary spacetime dimensions. Starting from the corresponding static spherically symmetric charged solutions, we obtain their dynamical…