arXiv subjects

B. Cuadros-Melgar

Publications and source records attributed to B. Cuadros-Melgar.

14 recordsLinked to original sources

arXiv2025

Black holes surrounded by massive vector fields in Kaluza-Klein gravity

We present an exact black hole solution surrounded by massive vector fields predicted by Kaluza-Klein (KK) gravity. KK gravity in four dimensions (4D) is of particular interest, as it predicts a tower of particle states, including gravitons with spin-0 and spin-1 components, in addition to the massless spin-2 gravitons of general relativity. The extra degrees of freedom in the gravitational sector modify the law of gravity, allowing the theory to explain the effects attributed to dark matter in the universe. In this paper, we construct a black hole solution surrounded by massive spin-1 gravitons within KK theory. In addition to the influence of the massive vector fields, we incorporate an interaction term between the black hole and the massive vector field. The black hole solution is affected by the mass of the spin-1 graviton and an additional parameter that encodes corrections to Newton's constant, as well as the coupling between the massive vector field and the black hole mass. We find that the coupling between the massive vector field and the black hole mimics the effect of an electric charge. To this end, we investigate the accretion disk, quasinormal modes (QNMs), and the stability of the black hole spacetime. Finally, we use Event Horizon Telescope (EHT) observations of Sgr A* to constrain the black hole parameters.

gr-qc↗

arXiv2024

Dark matter signatures of black holes with Yukawa potential

This study uses a nonsingular Yukawa--modified potential to obtain a static and spherically symmetric black hole solution with a cosmological constant. Such Yukawa--like corrections are encoded in two parameters, $α$ and $λ$, that modify Newton's law of gravity in large distances, and a deformation parameter $\ell_0$, which plays an essential role in short distances. The most significant effect is encoded in $α$, which modifies the total black hole mass with an extra mass proportional to $αM$, mimicking the dark matter effects at large distances from the black hole. On the other hand, the effect due to $λ$ is small for astrophysical values. We scrutinize the \textit{quasinormal} frequencies and shadows associated with a spherically symmetric black hole and the thermodynamical behavior influenced by the Yukawa potential. In particular, the thermodynamics of this black hole displays a rich behavior, including possible phase transitions. We use the WKB method to probe the \textit{quasinormal} modes of massless scalar, electromagnetic, and gravitational field perturbations. In order to check the influence of the parameters on the shadow radius, we consider astrophysical data to determine their values, incorporating information on an optically thin radiating and infalling gas surrounding a black hole to model the black hole shadow image. In particular, we consider Sgr A* black hole as an example and we find that its shadow radius changes by order of $10^{-9}$, meaning that the shadow radius of a black hole with Yukawa potential practically gives rise to the same result encountered in the Schwarzschild black hole. Also, in the eikonal regime, using astrophysical data for Yukawa parameters, we show that the value of the real part of the QNMs frequencies changes by $10^{-18}$.

gr-qc↗

arXiv2024

Charged Black Holes with Yukawa Potential

This study derives a novel family of charged black hole solutions featuring short- and long-range modifications. These ones are achieved through a Yukawa-like gravitational potential modification and a nonsingular electric potential incorporation. The short-range corrections encode quantum gravity effects, while the long-range adjustments simulate gravitational effects akin to those attributed to dark matter. Our investigation reveals that the total mass of the black hole undergoes corrections owing to the apparent presence of dark matter mass and the self-adjusted electric charge mass. Two distinct solutions are discussed: a regular black hole solution characterizing small black holes, where quantum effects play a crucial role, and a second solution portraying large black holes at considerable distances, where the significance of Yukawa corrections comes into play. Notably, these long-range corrections contribute to an increase in the total mass and hold particular interest as they can emulate the role of dark matter. Finally, we explore the phenomenological aspects of the black hole. Specifically, we examine the influence of electric charge and Yukawa parameters on thermodynamic quantities, the quasinormal modes for the charged scalar perturbations as well as for the vector perturbations, analysis of the geodesics of light/massive particles, and the accretion of matter onto the charged black hole solution.

gr-qc↗

arXiv2022

Gauss-Bonnet black holes in (2+1) dimensions: Perturbative aspects and entropy features

We investigate some aspects of the $(2+1)$-dimensional Gauss-Bonnet black hole proposed in [1][2]. The perturbations of scalar and massless spinorial fields are studied suggesting the dynamical stability of the geometry. The field evolution is analyzed calculating the quasinormal modes for different parameters and exploring the influence of the coupling constant of the theory. The hydrodynamical modes are also obtained in the small coupling limit. Furthermore, the entropy bound and the dominant semiclassical correction to the black hole entropy are calculated.

gr-qc↗

arXiv2021

Superradiance and instabilities in black holes surrounded by anisotropic fluids

In this paper we analyze the propagation of a charged scalar field in a Reissner-Nordström black hole endowed with one anisotropic fluid that can play the role of a cosmological term for certain set of parameters. The evolution of a scalar wave scattering is examined giving rise to the same superradiant scattering condition as in the de Sitter case. In addition, an analysis of the modes coming from the application of quasinormal boundary conditions is presented. Some special cases displaying analytical solutions for the quasinormal frequencies are discussed. Moreover, the superradiant condition is adapted to the quasinormal problem triggering unstable modes, what is confirmed by our numerical analysis.

gr-qc↗

arXiv2020

Analytical correspondence between shadow radius and black hole quasinormal frequencies

We consider the equivalence of quasinormal modes and geodesic quantities recently brought back due to the black hole shadow observation by Event Horizon Telescope. Using WKB method we found an analytical relation between the real part of quasinormal frequencies at the eikonal limit and black hole shadow radius. We verify this correspondence with two black hole families in $4$ and $D$ dimensions, respectively.

gr-qc↗

arXiv2020

Late-time tails, entropy aspects, and stability of black holes with anisotropic fluids

In this work we consider black holes surrounded by anisotropic fluids in four dimensions. We first study the causal structure of these solutions showing some similarities and differences with Reissner-Nordström-de Sitter black holes. In addition, we consider scalar perturbations on this background geometry and compute the corresponding quasinormal modes. Moreover, we discuss the late-time behavior of the perturbations finding an interesting new feature, i.e., the presence of a subdominant power-law tail term. Likewise, we compute the Bekenstein entropy bound and the first semiclassical correction to the black hole entropy using the brick wall method, showing their universality. Finally, we also discuss the thermodynamical stability of the model.

gr-qc↗

arXiv2019

Instability of Reissner-Nordström-AdS black hole under perturbations of a scalar field coupled to Einstein tensor

We study the instability of a Reissner-Nordström-AdS (RNAdS) black hole under perturbations of a massive scalar field coupled to Einstein tensor. Calculating the potential of the scalar perturbations we find that as the strength of the coupling of the scalar to Einstein tensor is increasing, the potential develops a negative well outside the black hole horizon, indicating an instability of the background RNAdS. We then investigate the effect of this coupling on the quasinormal modes. We find that there exists a critical value of the coupling which triggers the instability of the RNAdS. We also find that as the charge of the RNAdS is increased towards its extremal value, the critical value of the derivative coupling is decreased.

gr-qc↗

arXiv2019

Vectorial and spinorial perturbations in Galileon Black Holes: Quasinormal modes, quasiresonant modes and stability

In this work we have considered a model that includes the interaction of gravity and matter fields with Galilean invariance (the so-called derivative coupling) as well as some corresponding black hole type solutions. Quasinormal perturbations of two kinds of matter fields have been computed by different methods. The effect of the derivative coupling in the quasinormal spectrum has been analyzed and evaluated.

gr-qc↗

arXiv2013

Quasinormal modes and thermodynamical aspects of the 3D Lifshitz black hole

We consider scalar and spinorial perturbations on a background described by a $z=3$ three-dimensional Lifshitz black hole. We obtained the corresponding quasinormal modes which perfectly agree with the analytical result for the quasinormal frequency in the scalar case. The numerical results for the spinorial perturbations reinforce our conclusion on the stability of the model under these perturbations. We also calculate the area spectrum, which prove to be equally spaced, as an application of our results.

hep-th↗

arXiv2010

BTZ Solutions on Codimension-2 Braneworlds

We consider five-dimensional gravity with a Gauss-Bonnet term in the bulk and an induced gravity term on a 2-brane of codimension-2. We show that this system admits BTZ-like black holes on the 2-brane which are extended into the bulk with regular horizons.

hep-th↗

arXiv2008

Instability of the Time Dependent Horava-Witten Model

We consider scalar perturbations in the time-dependent Hourava-Witten Model in order to probe its stability. We show that during the non-singular epoque the model evolves without instabilities until it encounters the curvature singularity where a big crunch is supposed to occur. We compute the frequencies of the scalar field oscillation during the stable period and show how the oscillations can be used to prove the presence of such a singularity.

hep-th↗

arXiv2006

Stability and thermodynamics of brane black holes

We consider scalar and axial gravitational perturbations of black hole solutions in brane world scenarios. We show that perturbation dynamics is surprisingly similar to the Schwarzschild case with strong indications that the models are stable. Quasinormal modes and late-time tails are discussed. We also study the thermodynamics of these scenarios verifying the universality of Bekenstein's entropy bound as well as the applicability of 't Hooft's brickwall method.

gr-qc↗

arXiv2003

Thermal one- and two-graviton Green's functions in the temporal gauge

The thermal one- and two-graviton Green's function are computed using a temporal gauge. In order to handle the extra poles which are present in the propagator, we employ an ambiguity-free technique in the imaginary-time formalism. For temperatures T high compared with the external momentum, we obtain the leading T^4 as well as the subleading T^2 and log(T) contributions to the graviton self-energy. The gauge fixing independence of the leading T^4 terms as well as the Ward identity relating the self-energy with the one-point function are explicitly verified. We also verify the 't Hooft identities for the subleading T^2 terms and show that the logarithmic part has the same structure as the residue of the ultraviolet pole of the zero temperature graviton self-energy. We explicitly compute the extra terms generated by the prescription poles and verify that they do not change the behavior of the leading and sub-leading contributions from the hard thermal loop region. We discuss the modification of the solutions of the dispersion relations in the graviton plasma induced by the subleading T^2 contributions.

hep-th↗