244 citations · 1.9k across the 75 of their papers we have counts for
27 papers · 1 filter
In-Stabilities of massive white dwarfs in modified gravity
Ronaldo V. Lobato, Geanderson A. Carvalho, Neelima G. Kelkar +1
Super-Chandrasekhar white dwarfs are a timely topic in the last years in the scientific community due to its connection to supernovae type Ia (SN Ia). Some early studies tackled th…
Possible Connection between Dark Matter and Supermassive Black Holes
Davide Batic, Joud Mojahed Faraji, Marek Nowakowski
Dark Matter (DM) is usually studied in connection with rotational curves in the outskirts of the galaxies. However, the role of DM might be different in the galactic bulges and cen…
On the eigenvalues of the fermionic angular eigenfunctions in the Kerr metric
Davide Batic, Suzan Hamad Abdul Karim, Marek Nowakowski
In view of a result recently published in the context of deformation theory of linear Hamiltonian systems, we reconsider the eigenvalue problem associated to the angular equation a…
Massive white dwarfs in gravity
R. V. Lobato, G. A. Carvalho, N. G. Kelkar +1
In this work, we investigate the equilibrium configurations of massive white dwarfs (MWD) in the context of modified gravity, namely gravity, where stands for the Ri…
Rings of light caused by gravitational waves
Davide Batic, Joud Mojahed Faraji, Marek Nowakowski +1
We reconsider the case of the geodesic motion of a massive and massless beam of test particles in a gravitational wave. In particular, we use a direct Lagrangian approach which sim…
Non-singular non-flat universes
Andres Felipe Estupinan Salamanca, Sergio Bravo Medina, Marek Nowakowski +1
The quest to understand better the nature of the initial cosmological singularity is with us since the discovery of the expanding universe. Here, we propose several non-flat models…
Fuzzy dark matter black holes and droplets
Davide Batic, Deena Asem Abuhejleh, Marek Nowakowski
We consider the possibility of having Dark Matter (DM) black holes motivated by the Einasto density profile. This generalizes both the noncommutative mini black hole model and allo…
Light bending in a two black hole metric
M. Alrais Alawadi, D. Batic, M. Nowakowski
We discuss the propagation of light in the C-metric. We discover that null geodesics admit circular orbits only for a certain family of orbital cones. Explicit analytic formulae ar…
Perturbing microscopic black holes inspired by noncommutativity
Davide Batic, N. G. Kelkar, Marek Nowakowski +1
We probe into the instabilities of microscopic quantum black holes. For this purpose, we study the quasinormal modes (QNMs) for a massless scalar perturbation of the noncommutative…
Reply to "Comment on `Some exact quasinormal frequencies of a massless scalar field in Schwarzschild spacetime' ''
Davide Batic, Marek Nowakowski, Karlus Redway
We address the concerns raised by the author of "Comment: Some exact quasinormal frequencies of a massless scalar field in Schwarzschild spacetime" appeared in arXiv:1807.05940. In…
Viscous Cosmologies
Sergio Bravo Medina, Marek Nowakowski, Davide Batic
We probe into universes filled with Quark Gluon Plasma with non-zero viscosities. In particular, we study the evolution of a universe with non-zero shear viscosity motivated by the…
Einstein-Cartan Cosmologies
Sergio Bravo Medina, Marek Nowakowski, Davide Batic
Cosmologies based on General Relativity encompassing an anti-symmetric connection (torsion) can display nice desirable features as the absence of the initial singularity and the po…
Some exact quasi-normal frequencies of a massless scalar field in the Schwarzschild space-time
Davide Batic, Marek Nowakowski, Karlus Redway
We show that not all quasinormal modes of a massless scalar field in the Schwarzschild metric are encoded in the corresponding characteristic equation expressed by means of a conti…
The problem of embedded eigenvalues for the Dirac equation in the Schwarzschild black hole metric
Davide Batic, Marek Nowakowski, Kirk Morgan
We use the Dirac equation in a fixed black hole background and different independent techniques to demonstrate the absence of fermionic bound states around a Schwarzschild black ho…
Newtonian Cosmology with a Quantum Bounce
Pedro Bargueño, Sergio Bravo-Medina, Marek Nowakowski +1
It has been known for some time that the cosmological Friedmann equation deduced from General Relativity can be also obtained within the Newtonian framework under certain assumptio…
The Dirac equation in the Kerr-de Sitter metric
D. Batic, K. Morgan, M. Nowakowski +1
We consider a fermion in the presence of a rotating black hole immersed in a universe with positive cosmological constant. After deriving new formulae for the event, Cauchy and cos…
Orbiting phenomena in black hole scattering
D. Batic, N. G. Kelkar, M. Nowakowski
Rainbow, glory and orbiting scattering are usually described by the properties of the classical deflection function related to the real part of the quantum mechanical scattering ph…
On Born approximation in black hole scattering
D. Batic, N. G. Kelkar, M. Nowakowski
A massless field propagating on spherically symmetric black hole metrics such as the Schwarzschild, Reissner-Nordström and Reissner-Nordström-de Sitter backgrounds is considered. I…
Comment on "Quasinormal modes in Schwarzschild-de Sitter spacetime: A simple derivation of the level spacing of the frequencies"
D. Batic, N. G. Kelkar, M. Nowakowski
It is shown here that the extraction of quasinormal modes (QNMs) within the first Born approximation of the scattering amplitude is mathematically not well founded. Indeed, the con…
Velocity and velocity bounds in static spherically symmetric metrics
I. Arraut, D. Batic, M. Nowakowski
We find simple expressions for velocity of massless particles in dependence of the distance in Schwarzschild coordinates. For massive particles these expressions put an upper b…
The Minimum and Maximum Temperature of Black Body Radiation
M. Nowakowski, I. Arraut
We show, in different ways, that in the ubiquitous phenomenon of black body radiation there exists a minimum and maximum temperature. These limiting values are so small and large r…
Comparing two approaches to Hawking radiation of Schwarzschild-de Sitter black holes
I. Arraut, D. Batic, M. Nowakowski
We study two different ways to analyze the Hawking evaporation of a Schwarzschild-de Sitter black hole. The first one uses the standard approach of surface gravity evaluated at the…
The fate of a gravitational wave in de Sitter spacetime
M. Nowakowski, I. Arraut
If we want to explain the recently discovered accelerated stage of the universe, one of the option we have is to modify the Einstein tensor. The simplest such modification, in agre…
On the bound states of the Dirac equation in the extreme Kerr metric
Davide Batic, Marek Nowakowski
We study the eigenvalues of the angular equation arising after the separation of the Dirac equation in the extreme Kerr metric. To this purpose a self-adjoint holomorphic operator…