General Relativity and Quantum Cosmology
Using the thermodynamic approach introduced in e-Print: 2206.09124 [hep-th] to the case of Kerr-NUT solution, we demonstrate the existence of a new conserved quantity that is dual to the angular momentum, in the same way that the nut charge…
The present article deals with gravitational-wave propagation affected by higher-derivative terms that break spacetime symmetries. Two dimension-6 contributions of the gravitational Standard-Model Extension pose our starting point. A…
Can gravitational waves probe the near-horizon geometry of black holes, and if yes, which frequency scale is optimal? Although shorter wavelengths usually resolve smaller scales, we show that black-hole scattering may impose an…
Using approximately $5000$ numerical-relativity (NR) simulations spanning mass ratios up to $q=128$ and $1200$ black-hole-perturbation-theory (BHPT) simulations extending to $q=1000$, we present fully analytic models for the remnant…
In this paper, we investigate topologically charged Morris-Thorne-type traversable wormholes by solving the Einstein field equations with an anisotropic fluid as the energy-momentum tensor and analysing the resulting solutions. In…
We determine the small-oscillation period of a simple pendulum in Schwarzschild spacetime. After transients decay, the displaced rope coincides with a geodesic of the induced spatial metric. This determines the radial lift of the bob to…
The cosmological dynamics of generalized holographic Ricci dark energy (GHRDE) of Xu type, embedded within power-law $f(\mathcal{T})=\alpha\mathcal{T}+\beta\mathcal{T}^{m}$ teleparallel gravity and driven by the Hubble-parameter-dependent…
Spontaneous scalarization provides a dynamical mechanism to evade the no-hair paradigm, but it has been argued to generically eliminate the Cauchy horizon in charged black holes. We show that this obstruction is not universal, but instead…
We establish a sufficient one-minimum criterion for the off-shell Kerr family $\Delta(r) = r^2 - 2rm(r) + a^2$ with a positive, nondecreasing mass profile $m(r)$, showing that $1 - 2m'(r) - rm''(r) > 0$ ensures strict convexity and…
While General Relativity remains our most rigorously tested framework for gravitation, the theoretical persistence of singularities within standard black hole solutions continues to motivate the exploration of mathematically regular…
We consider a massive vector-field perturbation on a Kerr black hole background. We fix the field's density at the edge of the black hole sphere of influence to model a bath of wave cold dark matter, from which the black hole can accrete…
We study a massive scalar field on the rotating Kalb-Ramond black hole of Kumar, Ghosh and Wang, in the (near-)extremal corner of its three-parameter family $(a,\gamma,\lambda)$. We verify by direct substitution that the Klein-Gordon-Fock…
The entropy of the observable Universe is dominated, by fifteen orders of magnitude, by the horizons of supermassive black holes, and gravitational collapse into black holes has often been proposed as the Universe's preferred channel of…
Gravitational waves from compact binary coalescences and from early Universe processes are expected to form a gravitational-wave background. We employ a custom deep learning multi-scale multi-headed autoencoder architecture to isolate…
We investigate the null geodesic structure, photon sphere dynamics, and high-energy particle collisions within a class of static, spherically symmetric hairy Horndeski black holes. Characterized by an invariant metric root at $r = 2M$ and a…
Compact objects with the same exterior metric are locally indistinguishable to test particles, yet observables built from retarded fields can retain information about the spacetime outside the particle's immediate neighbourhood. The…
The entanglement entropy of quantum systems typically exhibits both ultraviolet and infrared (IR) divergences. In the low-frequency limit, the IR divergence is intimately tied to the unbounded spatial delocalization of zero-modes, a…
We compare the deviations of circular orbits in the nonrelativistic and relativistic cases. General solutions of the deviation equations are obtained. We find the potentials for the nonrelativistic case and the metric components in general…
This work investigates the brachistochrone problem for a traveler with constant local velocity within static and spherically symmetric (SSS) spacetimes. The brachistochrone trajectory (BT) equations for ultra-relativistic travelers are…
We investigate the excitation region of black hole quasinormal modes (QNMs) from both analytical and numerical perspectives. On the analytical side, we propose that the QNM excitation radius is identified by the dominance switching of WKB…