General Relativity and Quantum Cosmology
We develop a time-domain numerical framework for global scalar wave scattering in Minkowski spacetime. The main contribution is an exact conformal matching of three compactified regions: a past hyperboloidal domain attached to $\mathscr…
Previous work has developed the theory of linearized gravitational wave (GW) interactions with matter using the Bondi-Sachs formalism, but with the perturbations restricted to be quadrupolar, i.e., the angular dependence is spherical…
We generalise the quantum mechanical toy model for gravitationally induced decoherence presented in Xu, Blencowe (2022) and Domi et al. (2024). In contrast to earlier formulations, in which the Hamiltonian of the system of interest is…
Gravitational waves admit a Stokes decomposition into intensity ($I$), circular polarization ($V$), and linear polarization ($Q$, $U$), analogous to Cosmic Microwave Background (CMB) polarimetry. We implement a full-Stokes…
We investigate static, spherically symmetric (SS) spacetimes in covariant teleparallel \(F(T)\) gravity in the presence of electromagnetic sources. Starting from the coframe/spin-connection (CSC) pair formalism, we derive the field…
We calculate the gamma ray emission from a black-to-white hole transition. We put forward a model for the prompt emission phase, based on the photospheric emission model with the underlying idea that the number of photons and leptons…
We develop a fully automatic Mathematica implementation of the black-hole WKB method at very high orders based on the Bender-Wu algorithm, which in principle is limited only by memory and computational time, and show that when pushed to…
We investigated scalarization in dark matter stars. In scalar tensor theories, the coupling between matter and a scalar field generates an effective mass, which is known to trigger the growth of the scalar field in stars and black holes…
In this study, we explore the dynamics of particle orbits and their corresponding gravitational wave signatures in the vicinity of a Schwarzschild black hole (BH) surrounded by a cloud of strings and embedded in a perfect fluid dark matter…
Black-hole spectroscopy aims to infer properties of the remnant spacetime from the quasinormal-mode (QNM) spectrum of the gravitational-wave ringdown signal. In most implementations, however, this inference is performed with waveform models…
An exact gravitational instanton solution on a vacuum Kerr-like warped spacetime in conformal dilaton gravity is found. Remarkably, the metric solution results from a first-order PDE, allowing the connection with self-duality. The singular…
Gravitational waves (GWs) provide a powerful, theory-independent probe of the dynamical structure of spacetime and the cosmological background. We study linearized GW propagation in k-essence cosmology, where a non-canonical scalar field…
We study classical energy-condition admissibility for subluminal, positive-energy warp shells. For the constructions examined here, the energy-condition failures are localized at the smooth source--vacuum transition rather than in the bulk…
In this work, we investigate the thermodynamic properties, Hawking-radiation sparsity, and greybody-factor bounds of a hairy Kiselev black hole surrounded by a quintessential fluid. The spacetime geometry contains, in addition to the…
Regular black holes (RBHs) can be seen as possible alternatives to standard black holes (BHs), since these geometries do not have a curvature singularity. As a way of improving our knowledge of such geometries, we can investigate how the…
We investigate the particle motion around a Schwarzschild black hole immersed in a swirling Bertotti-Robinson-Bonnor-Melvin background. This spacetime provides a physically well-motivated framework for studying how the two different…
Generalized Proca theory supplements gravity with a massive vector field whose derivative self-interactions can support black holes carrying primary vector hair. In the asymptotically de Sitter branch considered here, the de Sitter scale is…
We investigate the field-theoretic realization of regular black holes sourced by dark matter halo profiles within nonlinear electrodynamics (NED) minimally coupled to gravity. Starting from a static, spherically symmetric geometry…
The physical origin of spacetime discreteness remains a central open problem in quantum gravity, with most existing approaches relying on specific microscopic structures or model-dependent assumptions. In this letter, spacetime discreteness…
The ringdown of a perturbed black hole (BH) can be described as a superposition of quasinormal modes (QNMs), whose frequencies are determined by the spacetime geometry while their amplitudes depend also on the perturbing source. However,…