General Relativity and Quantum Cosmology

We revisit the inter-detector cross-correlation criterion used in gravitational-wave validation by extending the analysis of Creswell et al.~\cite{Creswell2017} to nine LIGO--Virgo candidate events from the O2 and O3 observing runs. For…

We compute the stochastic background of gravitational waves (GWs) produced at second order in cosmological perturbation theory by a primordial curvature power spectrum that is flat in $\ln k$ over a finite band…

We study linear perturbations of static, spherically symmetric solutions of scalar-tensor theories (STT) of gravity from the Bergmann-Wagoner-Nordtvedt class, sourced by nonlinear electrodynamics (NED). We obtain a general expression for…

We construct a new family of asymptotically flat static and rotating regular black holes characterized by a Minkowskian core and a finite two-horizon structure. The solutions are obtained within the framework of gravitational decoupling and…

In this paper, we consider possible corrections to the characteristics of inflationary models based on a specific parametrization of the non-minimal coupling between the scalar field and curvature. At the inflationary stage, these…

A photon coupled non-minimally to the Weyl tensor propagates differently in its two linear polarization states: the vacuum around a black hole becomes a birefringent medium. On a Schwarzschild background the coupling $\alpha$ splits the…

Scalarizations of the Einstein-Euler-Heisenberg (EEH) black hole (EEHBH) with multiple horizons are investigated in the EEH-scalar theory by introducing a quadratic scalar coupling to the Maxwell term. For mass $M=1$ and Euler-Heisenberg…

We propose a novel way to achieve the regularization of the JNW globally naked singularity sourced by the canonical Einstein minimally coupled scalar field (EMS). The key idea is to complexify (Wick rotate) the JNW parameters, which yields…

Determining whether Planck-scale effects can stabilize black holes addresses fundamental questions about black hole evaporation and quantum gravity consistency. Here, we analyze the thermodynamic topology of Schwarzschild black holes under…

Recently, a new exact Ricci-flat rotating black-hole solution was constructed in four-dimensional general relativity, in which an additional parameter $B$ characterizes a spindle deformation of the Kerr geometry. We study geodesic motion…

We study the motion of massive (un)charged test particles in space-times of electric and dyonic black holes which carry scalar hair. We determine the stable and unstable circular orbits and discuss the collision of massive test particles.…

Despite compelling evidence, the absence of a confirmed dark matter particle has sustained interest in modified gravity as an alternative explanation for the observed phenomenology. One prominent example is Modified Newtonian Dynamics…

We attempt to magnetise the de Sitter (dS) and Anti-de Sitter (AdS) spacetimes in spherical symmetry. First, the weak field case is considered where Maxwell's equation is solved to find magnetic fields in fixed dS/AdS backgrounds. For…

In this work, we explore the quasinormal modes (QNMs) of the Bonanno-Reuter black hole, one of the first regular black hole metric suggested by the Asymptotically Safe Gravity (ASG) program. The running parameter $\alpha$ is set to a…

We study scalar and vector bosons in the Bonnor--Melvin--$\Lambda$ spacetime within the Duffin--Kemmer--Petiau (DKP) formalism. By employing Umezawa's projection operators, we separate the physical spin-0 and spin-1 sectors and derive the…

In this paper, we establish a geometric correspondence between the Lorentzian Raychaudhuri equation and Perelman's non-collapsing theorem for the Ricci flow. By interpreting the Raychaudhuri equation as a Lorentzian analogue of Ricci flow,…

We investigate massive scalar perturbations of Kerr-Newman black holes, focusing on the $(\ell,m) = (1,1)$ quasinormal mode spectrum in the near-extremal regime. We identify a sequence of exceptional lines, at which overtone frequencies…

Einstein's theory of general relativity (GR) has been remarkably successful in describing gravitational phenomena. However, several open questions in modern cosmology and astrophysics (e.g. inflation, dark energy) suggest the need for…

We present GRACE, a new GPU-accelerated numerical-relativity framework designed to run efficiently on heterogeneous high-performance computing platforms. Developed from scratch and built exclusively on open-source libraries, GRACE employs…

We study electro-acoustic perturbative modes in homogeneous, isotropic and expanding -- dubbed as Friedmann-Lemaitre-Robertson-Walker (FLRW) -- Jellium models, thereby mimicking density perturbations in analogous Newtonian cosmological…