General Relativity and Quantum Cosmology
This article reviews a Hamiltonian framework for describing Dirac fermions propagating on quantum cosmological spacetimes within loop quantum cosmology. Expanding the fermionic field in spinor harmonics on a closed…
We study electromagnetic wave propagation in metric--affine geometries, where torsion and non-metricity may be present and the coupling between electromagnetism and spacetime is no longer unique. Rather than choosing a particular coupling…
We investigate an extended cosmological scenario based on the Barrow-Tsallis entropy, incorporating a varying (i.e., energy-scale-dependent) anomalous dimension. This behavior is reminiscent of quantum gravity and effective field theory…
A static configuration consisting of a rigid spherical shell enclosing a degenerate Schwarzschild Klinkhamer wormhole is investigated in general relativity. The shell is analyzed using the Israel junction conditions, while the total ADM…
The persistent $H_0$ and $S_8$ tensions motivate the search for new dark-energy mechanisms capable of modifying the late-time expansion history while preserving the successful early-Universe predictions of $\Lambda$CDM scenario.…
In this paper we propose that spacetime is an emergent fractal geometry generated by the entanglement structure of an underlying quantum information network. Indeed, it is developed a framework in which spacetime, quantum mechanics, and…
The growing sensitivity of gravitational-wave detectors enables increasingly precise tests of black hole (BH) ringdown spectroscopy. BH quasinormal modes (QNMs) are, however, spectrally unstable: small near-horizon modifications can produce…
We analytically determine the leading backreaction of a spherically symmetric massive complex scalar quasi-bound state (with mass $\mu$) on a Schwarzschild black hole with (initial) gravitational radius $r_0$. Working in the small-coupling…
General Relativistic Entropic Acceleration (GREA) attributes the late-time acceleration of the Universe to the entropy growth of the causal cosmological horizon, without a cosmological constant, with a phenomenology fixed by the single…
The investigation of possible quantum-gravity effects in cosmology is of considerable interest, especially when such effects can be tested against observations of the late-time expansion. In the present work we study a quadratic…
We investigate scalar perturbations of the static loop quantum black bounce (LQBB) spacetime with multipole index $l=1$, focusing on time-domain signals and fundamental quasinormal frequencies (QNFs). The LQBB model provides a unified…
We show that the Levi-Civita connection for the Taub-NUT metric is singular on Misner strings and generates an Einstein tensor containing the squares of the delta function. This can be improved by introducing torsion, in which case the…
Conserved gravitational charges are commonly expressed as surface integrals of the metric perturbation and its first derivatives. We show that, in the usual asymptotically AdS and asymptotically flat settings, the standard charges admit…
The strong deflection limit (SDL) of the deflection angle is well established for general spherically symmetric spacetimes, but a systematic SDL treatment of spin precession has been lacking. We derive the SDL expansion for the spin…
This contribution considers constraints from analyses of gravitational wave data from binary black hole coalescence, on possible corrections to the Bekenstein-Hawking Area Formula for black hole entropy. Most recent analyses of…
The gravitational baryogenesis is studied in regularized four dimensional Einstein Gauss Bonnet model with rainbow gravity corrections. This combined framework generates a non vanishing time derivative of the Ricci scalar even during…
Deformations of sandwich gravitational waves are considered. Squeezing a wave with pure displacement (DM) parameters to an impulsive wave, the DM property is lost, leaving us with the velocity effect (VM). For each fixed value of the…
This paper investigates how to extract energy from a non-Kerr rotating spacetime with an anomalous quadrupole moment via the magnetic reconnection mechanism. Unlike many other rotating spacetimes, this spacetime possesses closed timelike…
Modifications to General Relativity can significantly alter the perturbative response of black holes, leaving imprints on quasinormal-mode spectra, waveform amplitudes and phases, and late-time tails. The parametrized beyond-Teukolsky…
The frequent presence of non-Gaussian transient noise, or glitches, in gravitational-wave detector data can affect gravitational-wave searches, parameter estimation, and downstream analyses. To identify and mitigate transient noise near…