arXiv subjects

Almendra Aragón

Publications and source records attributed to Almendra Aragón.

5 recordsLinked to original sources

arXiv2021

Scalar quasinormal modes for 2+1-dimensional Coulomb like AdS black holes from non lineal electrodynamics

We study the propagation of scalar fields in the background of $2+1$-dimensional Coulomb like AdS black holes, and we show that such propagation is stable under Dirichlet boundary conditions. Then, we solve the Klein-Gordon equation by using the pseudospectral Chevyshev method, and we find the quasinormal frequencies. Mainly, we find that the quasinormal frequencies are purely imaginary for a null angular number and they are complex and purely imaginary for a non null value of the angular number, which depend on the black hole charge, angular number and overtone number. On the other hand, the effect of the inclusion of a Coulomb like field from non lineal electrodynamics to General Relativity for a vanishing angular number is the emergence of two branches of quasinormal frequencies in contrast with the static BTZ black hole.

gr-qc↗

arXiv2021

Quasinormal modes and their anomalous behavior for black holes in $f(R)$ gravity

We study the propagation of scalar fields in the background of an asymptotically de-Sitter black hole solution in $f(R)$ gravity. The aim of this work is to analyze in modified theories of gravity the existence of an anomalous decay rate of the quasinormal modes (QNMs) of a massive scalar field which was recently reported in Schwarzschild black holes backgrounds, in which the longest-lived modes are the ones with higher angular number, for a scalar field mass smaller than a critical value, while that beyond this value the behavior is inverted. We study the QNMs for various overtone numbers and they depend on a parameter $β$ which appears in the metric and characterizes the $f(R)$ gravity. For small $β$, i.e small deviations from the Schwarzschild-dS black hole the anomalous behaviour in the QNMs is present for the photon sphere modes, and the critical value of the mass of the scalar field depends on the parameter $β$ while for large $β$, i.e large deviations the anomalous behaviour and the critical mass does not appear. Also, the critical mass of the scalar field increases when the overtone number increases until the $f(R)$ gravity parameter $β$ approaches the near extremal limit at which the critical mass of the scalar field does not depend anymore on the overtone number. The imaginary part of the quasinormal frequencies is always negative leading to a stable propagation of the scalar fields in this background.

gr-qc↗

arXiv2021

Massive Dirac quasinormal modes in Schwarzschild-dS black holes: anomalous decay rate and fine structure

Recently, the anomalous decay rate of quasinormal modes has been studied for some geometries under scalar field perturbations, which occurs when the longest-lived modes are the ones with higher angular number, as well as, the existence of a critical scalar field mass, i.e the value of scalar field mass such that the decay rate does not depend appreciably on the angular number, and beyond which the behaviour of the decay rate is inverted. Here, we consider the propagation of fermionic fields in the background of Schwarzschild de Sitter black holes, and we show that the anomalous decay rate behaviour and the fine structure, related to the coupling between the chirality and the mass of the field, can be observed in the fermionic spectrum.

gr-qc↗

arXiv2020

Anomalous decay rate of quasinormal modes in Schwarzschild-dS and Schwarzschild-AdS black holes

Recently an anomalous decay rate of the quasinormal modes of a massive scalar field in Schwarzschild black holes backgrounds was reported in which the longest-lived modes are the ones with higher angular number, for a scalar field mass smaller than a critical value, while that beyond this value the behaviour is inverted. In this work, we extend the study to other asymptotic geometries, such as, Schwarzschild-de Sitter and Schwarzschild-AdS black holes. Mainly, we found that such behaviour and the critical mass are present in the Schwarzschild-de Sitter background. Also, we found that the value of the critical mass increases when the cosmological constant increases and also when the overtone number is increasing. On the other hand, despite the critical mass is not present in Schwarzschild-AdS black holes backgrounds, the decay rate of the quasinormal modes always exhibits an anomalous behaviour.

gr-qc↗

arXiv2020

Perturbative and nonperturbative quasinormal modes of 4D Einstein-Gauss-Bonnet black holes

We study the propagation of probe scalar fields in the background of 4D Einstein-Gauss-Bonnet black holes with anti-de Sitter (AdS) asymptotics and calculate the quasinormal modes. Mainly, we show that the quasinormal spectrum consists of two different branches, a branch perturbative in the Gauss-Bonnet coupling constant $α$ and another branch nonperturbative in $α$. The perturbative branch consists of complex quasinormal frequencies that approximate to the quasinormal frequencies of the Schwarzschild AdS black hole in the limit of a null coupling constant. On the other hand, the nonperturbative branch consists of purely imaginary frequencies and is characterized by the growth of the imaginary part when $α$ decreases, diverging in the limit of null coupling constant, therefore they do not exist for the Schwarzschild AdS black hole. Also, we find that the imaginary part of the quasinormal frequencies is always negative for both branches; therefore, the propagation of scalar fields is stable in this background.

gr-qc↗