General Relativity and Quantum Cosmology
Strong evidence for an isotropic, Gaussian gravitational wave background (GWB) has been found by multiple pulsar timing arrays (PTAs). The GWB is expected to be sourced by a finite population of supermassive black hole binaries (SMBHBs)…
We study the geodesic structure and observable properties of asymptotically flat regular black holes sourced by a phantom scalar field characterized by a scalar charge $A$. This parameter removes the central singularity and continuously…
Astrophysical black holes are usually surrounded by an accretion disk. At least parts of these accretion disks consist of a plasma in which light rays with different energies are dispersed. However, we usually do not know the exact…
In this work we study a scale invariant gravity theory containing two scalar fields, dust particles and a measure defined from degrees of freedom independent of the metric. The integration of the degrees of freedom that define the measure…
We develop a class of regular black holes by prescribing finite curvature invariants and reconstructing the corresponding spacetime geometry. Two distinct approaches are employed: one based on the Ricci scalar and the other on the Weyl…
This work explores the intersection of quantum mechanics and curved spacetime by employing the Wigner formalism to investigate quantum systems in the vicinity of black holes. Specifically, we study the quantum dynamics of a probe particle…
In this paper we propose a novel unified cosmological model that connects a pre-inflationary epoch, starting at the Planckian time, with the onset of inflation within a single scalar-field framework. The pre-inflationary phase is…
The article deals with the role of gravitational radiation energy in the large-scale dynamics of the universe. Motivated by the observed accelerated expansion, we investigate whether gravitational energy, treated as a well-defined physical…
We study the scattering of charged massive particles impinging on a Reissner-Nordstr\"{o}m (RN) black hole immersed in perfect fluid dark matter (PFDM). We obtain an approximation of absorption cross section in the low-frequency regime via…
Motivated by their relevance to the interior of nonrotating black holes, classical and quantum Kantowski-Sachs cosmologies have recently attracted increasing attention. This interest has led to the development of a Hamiltonian formalism for…
Unifying the early-universe inflationary paradigm with late-time cosmic acceleration, while resolving the initial Big Bang singularity, remains one of the most profound challenges in modern cosmology. In this paper, we propose a…
Within general relativity, black holes are widely regarded as the ultimate benchmark for compactness in the Universe. Recently, however, neutron star models have been constructed in a higher-curvature theory -- quasi-topological gravity…
For electromagnetism in Minkowski spacetime, the Bessel-Hagen method gives a particularly direct Noetherian derivation of the standard gauge-invariant energy-momentum tensor. The key step is to supplement the form variation generated by an…
This paper reports a study on the formation and physical characteristics of compacts stars in AdS spacetime within the framework of Bose-Einstein Condensate. Considering a Bose-Einstein condensate background at zero temperature this study…
We investigate the finite-time instability of massive spinning test particles around a rotating hairy black hole generated through gravitational decoupling. The particle motion is described by the full Mathisson-Papapetrou-Dixon equations…
Recently, it was discussed how the presence of a Killing horizon induces decoherence on a quantum system in a superposition of states. Focusing on the case of an electrically-charged system with superposed positions, this would happen due…
We show that chain-like transients in head-on collisions of radially excited boson stars are controlled by the binary collision time, not by radial excitation alone. For selected \(n=2\), \(\lambda=400\) self-interacting configurations,…
This paper investigates the appearance characteristics of static black holes embedded in Dehnen-(1,4,5/2)-type dark matter halos with a quintessential field, focusing on how the dark matter halo and dark energy affect the black hole images.…
Recently, we showed that the possibility of an interstellar mission to the closest black hole, while highly speculative and extremely challenging, is not completely unrealistic within the next few decades. Since such a mission might last…
Gravitational-wave observations of merging binary neutron stars and black holes are now routinely made by detectors in the Advanced LIGO-Virgo-KAGRA network. Neutron star binary systems may also produce detectable electromagnetic and…