9 research outputs found
Formation and Stability of Area Quantized Black Holes
We investigate the ergoregion instability of area-quantized rotating quantum
black holes (QBH) under gravitational perturbation. We show that the
instability can be avoided in binary systems that include QBHs if the
separation between the inspiralling components at the onset of black hole
formation is less than a critical value. We also analyze the formation history
of such systems from stellar progenitors and demonstrate that a significant
fraction of progenitor masses cannot lead to QBH formation, making it unlikely
for LIGO-Virgo black hole binaries to comprise rotating QBHs.Comment: 8 pages, 6 figures, numerical codes will be made available upon
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Test of the Second Postulate of Relativity from Gravitational Wave Observations
The second postulate of special relativity states that the speed of light in
vacuum is independent of the emitter's motion. Though this claim has been
verified in various experiments and observations involving electromagnetic
radiation with very high accuracy, such a test for gravitational radiation
still needs to be explored. We analyzed data from the LIGO and Virgo detectors
to test this postulate for gravitational radiation within the ambit of
\textit{emission models}, where the speed of gravitational waves emitted by a
source moving with a velocity relative to a stationary observer is given by
, where is a constant. We have estimated the upper bound
on the 90\% credible interval over that parameterizes the deviation from
the second postulate to be which is several
orders of magnitude more stringent compared to previous bounds obtained from
electromagnetic observations. The Bayes' factor supports the second postulate,
with very strong evidence that the data is consistent with the null hypothesis
. This confirms that the speed of gravity is independent of the motion
of the emitter, upholding the principle of relativity for gravitational
interactions.Comment: 7 pages, 3 figure
Overcharging higher curvature black holes
by Rajes Ghosh, C. Fairoos and Sudipta Sarka
Regularized stable Kerr black hole: cosmic censorships, shadow and quasi-normal modes
Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may model theory-agnostic phenomenological black holes that bypass the aforesaid issues. These so-called regular black holes are extensively studied in the literature using parameterized modifications over the black hole solutions of general relativity. However, since there exist several ways to model such black holes, it is important to study the consistency and viability of these solutions from both theoretical and observational perspectives. In this work, we consider a recently proposed model of regularized stable rotating black holes having two extra parameters in addition to the mass and spin of a Kerr solution. We start by computing their quasi-normal modes under scalar perturbation and investigate the impact of those additional parameters on black hole stability. In the second part, we study shadows of the central compact objects in and modelled by these regularized black holes and obtain stringent bounds on the parameter space requiring consistency with Event Horizon Telescope observations
Quasi-normal modes of non-separable perturbation equations: the scalar non-Kerr case
International audienceScalar, vector and tensor perturbations on the Kerr spacetime are governed by equations that can be solved by separation of variables, but the same is not true in generic stationary and axisymmetric geometries. This complicates the calculation of black-hole quasi-normal mode frequencies in theories that extend/modify general relativity, because one generally has to calculate the eigenvalue spectrum of a two-dimensional partial differential equation (in the radial and angular variables) instead of an ordinary differential equation (in the radial variable). In this work, we show that if the background geometry is close to the Kerr one, the problem considerably simplifies. One can indeed compute the quasi-normal mode frequencies, at least at leading order in the deviation from Kerr, by solving an ordinary differential equation subject to suitable boundary conditions. Although our method is general, in this paper we apply it to scalar perturbations on top of a Kerr black hole with an anomalous quadrupole moment, or on top of a slowly rotating Kerr background
Quasi-normal modes of non-separable perturbation equations: the scalar non-Kerr case
International audienceScalar, vector and tensor perturbations on the Kerr spacetime are governed by equations that can be solved by separation of variables, but the same is not true in generic stationary and axisymmetric geometries. This complicates the calculation of black-hole quasi-normal mode frequencies in theories that extend/modify general relativity, because one generally has to calculate the eigenvalue spectrum of a two-dimensional partial differential equation (in the radial and angular variables) instead of an ordinary differential equation (in the radial variable). In this work, we show that if the background geometry is close to the Kerr one, the problem considerably simplifies. One can indeed compute the quasi-normal mode frequencies, at least at leading order in the deviation from Kerr, by solving an ordinary differential equation subject to suitable boundary conditions. Although our method is general, in this paper we apply it to scalar perturbations on top of a Kerr black hole with an anomalous quadrupole moment, or on top of a slowly rotating Kerr background
Quasi-normal modes of non-separable perturbation equations: the scalar non-Kerr case
International audienceScalar, vector and tensor perturbations on the Kerr spacetime are governed by equations that can be solved by separation of variables, but the same is not true in generic stationary and axisymmetric geometries. This complicates the calculation of black-hole quasi-normal mode frequencies in theories that extend/modify general relativity, because one generally has to calculate the eigenvalue spectrum of a two-dimensional partial differential equation (in the radial and angular variables) instead of an ordinary differential equation (in the radial variable). In this work, we show that if the background geometry is close to the Kerr one, the problem considerably simplifies. One can indeed compute the quasi-normal mode frequencies, at least at leading order in the deviation from Kerr, by solving an ordinary differential equation subject to suitable boundary conditions. Although our method is general, in this paper we apply it to scalar perturbations on top of a Kerr black hole with an anomalous quadrupole moment, or on top of a slowly rotating Kerr background