General Relativity and Quantum Cosmology
We study the effect of shear viscosity in stationary magnetized accretion tori on synthetic images of non-rotating black hole shadows. Shear viscosity and spacetime-curvature contributions are introduced perturbatively in the tori through…
This manuscript investigates the impact of bulk viscosity on the viability of cosmic bounce solutions in the context of $f(\mathcal{Q})$ theory, where $\mathcal{Q}$ is a non-metricity scalar. To complete this objective, we study the…
The cosmic microwave background radiation or particles surrounding a black hole can be modeled as a thermal bath coupled to the black hole. In this study, we investigate the effects of such a thermal bath on black hole radiation. The model…
Scattered light is a relevant noise source in current ground-based gravitational-wave detectors and a critical design concern for next-generation observatories. Beamtube scattered light estimates usually combine optical propagation…
Gravitational wave astronomy provides an exemplary avenue to study exotic compact stars with utmost precision. Recent analyses of GW170817 have reported possible post-merger gravitational wave echoes with a significance of $4.2\sigma$ and a…
The signals from the LIGO-Virgo-KAGRA network of gravitational-wave (GW) detectors allow us to perform sensitive tests of general relativity (GR) in the dynamical and strong-field regime of gravity. We present the results of seven tests of…
From 10 April 2024 15:00 UTC to 18 November 2025 16:00 UTC, the AdvancedVirgo+ gravitational wave detector participated in the LIGO-Virgo-KAGRA O4 observing run, started on 24 May 2023 15:00 UTC. Around 173 transient gravitational wave (GW)…
We study the optical appearance of a rotating regular Bardeen black hole embedded in perfect fluid dark matter (PFDM) when photon propagation occurs through a plasma medium. Three plasma models are examined: a homogeneous distribution, a…
We report on a stationary solution of the four-dimensional vacuum Einstein equations, which describes a Lorentzian wormhole harboring two antipodal co-rotating black holes. These are hung from the ``other'' spacelike infinity by two…
Whether the principles of general relativity extend to a quantum regime remains one of the open questions in modern physics. In classical general relativity, Einstein's equivalence principle underpins the interpretation of gravity as…
We study the finite-time accretion of complex massive scalar wave packets by a Schwarzschild black hole in the test-field regime, with parameters motivated by ultralight fuzzy dark matter around supermassive black holes. Our goal is to…
Exotic compact objects (ECOs) may produce late-time gravitational-wave (GW) echoes, but sufficiently compact ECOs undergoing realistic accretion may eventually form an event horizon. We investigate the evolution of quasinormal modes and GW…
We study higher-rank generalized Killing tensors with mixed symmetries, providing a couple of examples and applications. It is shown that such objects naturally exist in higher-dimensional rotating black hole spacetimes, where they arise as…
The frozen star is a model for the interior of an astrophysical black hole that is externally indistinguishable from the singular geometry of a Schwarzschild black hole, even though it contains no singularities nor trapped surfaces. The…
We investigate the tidal properties of static neutron stars in the Neves--Gardim branch of bumblebee gravity, a vector--tensor theory in which a nonzero vacuum expectation value of the bumblebee field spontaneously breaks local Lorentz…
We consider the model of the regular black hole, which demonstrates that the gravastar is thermodynamically unstable towards the Schwarzschild black hole with singularity.
The Johannsen-Psaltis (JP) metric is constructed by introducing deviation parameters into the Kerr metric. The presence of these deviation parameters provides additional degrees of freedom for testing the extent to which astrophysical black…
We construct a locally scale-invariant formulation of Schr\"{o}dinger geometry in symmetric teleparallel gravity. The unique scale transformation preserving autoparallelism, torsionlessness and the Schr\"{o}dinger affine structure is first…
Matched filtering remains the most sensitive method for detecting gravitational waves from compact binary coalescences. The efficiency of such searches depends on how well a discrete template bank covers the underlying parameter space.…
Timelike geodesics, periodic orbits, and their associated gravitational-wave signatures are examined in the spacetime of a Bonanno--Reuter regular black hole, a geometry arising from Asymptotically Safe Gravity in which a running Newton…