arXiv subjects

L. A. López

Publications and source records attributed to L. A. López.

At least 19 recordsLinked to original sources

arXiv2026

Red/Blue shifts of photons in a Hayward black hole immersed in perfect fluid dark matter

We investigate the red/blue shifts of photons emitted by particles moving along stable circular orbits around a Hayward black hole immersed in perfect fluid dark matter (PFDM). The PFDM contribution modifies the horizon structure and shifts the characteristic radii associated with circular motion, including the photon sphere and the ISCO radius. The corresponding redshift and blueshift are found to be sensitive to both the magnitude and sign of the PFDM parameter, providing potentially observable signatures of the surrounding dark matter distribution. Finally, we analyze the black hole shadow and compare its size with the observational constraints from Sgr A*. Positive values of the PFDM parameter reduce the shadow radius, whereas negative values produce larger deviations from the Schwarzschild case, suggesting that shadow observations may constrain the PFDM contribution.

gr-qc↗

arXiv2026

Constrained thermodynamics and geodesic observables of an effective non-commutative Kerr-like black hole

We investigate the horizon structure, constrained thermodynamics, and geodesic properties of an effective Kerr-like black hole in a non-commutative background. Deformation modifies the radial geometry through a mass-dependent charge-like contribution, while preserving the separability of the geodesic equations. We determine the conditions for horizon existence, identify the extremal zero-temperature configuration, and analyze the stationary-limit surfaces and the ergoregion. Special attention is paid to the thermodynamic interpretation of the model, where the geometric Hawking quantities are distinguished from the conjugate variables associated with the constrained state space at fixed non-commutative deformation parameter. The canonical and grand-canonical heat capacities are derived to characterize their ensemble-dependent local thermal behavior. We also obtain the spherical photon region, equatorial light rings, and shadow boundary, showing that the deformation shifts the characteristic photon orbits inwards and reduces the overall size of the shadow. Timelike circular motion is studied through the innermost stable circular orbit, where non-commutative correction produces an inward shift of both the prograde and retrograde branches. Finally, invariant photon frequency shifts are obtained by treating the emitter's orbital direction and the photon's tangential emission direction as independent physical choices.

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arXiv2026

Scattering and absorption sections by an improved Schwarzschild black hole

In this contribution, we investigate the scattering and absorption sections of the improved Schwarzschild black hole. The differential scattering section is analysed using three complementary approaches: the classical approximation, the semi-classical approximation, and the partial wave technique. We show that, while the classical scattering section exhibits only small deviations from the standard Schwarzschild case, the semi-classical and partial wave analyses reveal differences in the interference pattern and in the amplitude. Also, the absorption section is computed using the partial wave method and compared with the sinc approximation. We find that both approaches present deviations that appear in the low-frequency regime, where the partial wave result approaches the horizon area. Our results indicate that quantum corrections in the Schwarzschild can lead to modifications in scattering and absorption properties, providing further insight into the phenomenology of quantum corrected black holes.

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arXiv2026

Quasi-normal modes of the Ayón-Beato-García black hole surrounded by quintessence

We compute the quasi-normal modes of scalar, electromagnetic, and gravitational perturbations of an Ayón-Beato-García black hole surrounded by quintessence using the Asymptotic Iteration Method (30 iterations). The results are compared with the WKB approximation to evaluate the robustness and accuracy of AIM. The results show that the real part of the frequencies increases with the charge parameter, while the absolute value of the imaginary part decreases as the charge parameter increases. In contrast, both the real part and the absolute value of the imaginary part decrease as the quintessence parameter $c$ increases. These trends are observed for both values of the quintessence state parameter, $ω_q=-2/3$ and $ω_q=-4/9$; however, the effects become more pronounced as $ω_q$ approaches $-1$ corresponding to cosmological constant. The quasi-normal frequencies tend to have finite values, which could facilitate their observational detection. Moreover, the presence of quintessence leads to a slower damping of the perturbations.

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arXiv2026

Scattering sections from regular black holes immersed in perfect fluid dark matter

In this contribution, we investigate the scattering cross sections of black holes immersed in perfect fluid dark matter (PFDM). We present both the classical and semi-classical scattering cross sections for different values of the parameter that characterizes the PFDM contribution. Our results show that the presence of dark matter increases the classical scattering cross section and modifies the width of the interference fringes in the semi-classical regime. In addition, the scattering cross section is also computed using the partial wave method for the black holes considered, exhibiting similar qualitative behavior. These findings suggest that the effects of dark matter surrounding black holes may play an important role in black holes phenomenology, particularly in certain regions near the black hole.

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arXiv2026

Quasi-normal modes and absorption section from regular black holes immersed in perfect fluid dark matter

We study scalar, electromagnetic and gravitational perturbations of three families of regular black holes, Hayward, Bardeen, and Ayon-Beato-García immersed in a Perfect Fluid Dark Matter (PFDM) background. Using both the sixth-order WKB approximation and the Asymptotic Iteration Method (AIM), we determine the corresponding quasi-normal modes and absorption cross sections. By fixing the horizon radius, we analyze the dependence of the parameters of the black holes and the parameter of PFDM. The computed quasi-normal modes confirm the dynamical stability of the black holes under scalar, electromagnetic and gravitational perturbations. Furthermore, both the real and imaginary parts of the quasi-normal modes increase with the multipole number $l$, corresponding to higher oscillation frequencies and faster damping rates. On the other hand, absorption cross sections are compared under similar parametric conditions. The results demonstrate that PFDM influences the dynamical properties of regular black holes.

gr-qc↗

arXiv2025

Spectral analysis of Dirac materials in position-dependent magnetic and electric fields via Heun functions

This work focuses on the study of the spectral problem for Dirac materials immersed in position-dependent magnetic and electric fields. To achieve this, the system of differential equations satisfied by the eigenfunction components of the Hamiltonian has been decoupled, and the solutions for some specific cases have been analyzed using Heun functions, which provide us with a quantization relation and allow us to determine the solutions for the bound states.

math-ph↗

arXiv2024

Quasinormal modes of the Schwarzschild black hole with a deficit solid angle and quintessence-like matter: Improved asymptotic iteration method

We study the quasinormal modes (QNM) for scalar, and electromagnetic perturbations in the Schwarzschild black hole with a deficit solid angle and quintessence-like matter. Using the sixth--order WKB approximation and the improved asymptotic iteration method (AIM) we can determine the dependence of the quasinormal modes on the parameters of the black hole and the parameters on the test fields. The values of the real part and imaginary parts of the quasi--normal modes increase with the decrease of the values of the deficit solid angle and density of quintessence-like matter. The quasinormal modes gotten by these two methods are in good agreement. Using the finite difference method, we obtain the time evolution profile of such perturbations in this Black Hole.

gr-qc↗

arXiv2022

Quasinormal modes of a Generic-class of magnetically charged regular black hole: scalar and electromagnetic perturbations

In this contribution, we study the quasinormal modes of a Generic--class of a regular black hole with a magnetic charge in nonlinear electrodynamics, considering scalar and electromagnetic perturbations. The Generic--class contains the Bardeen--class, Hayward--class, and New--class solutions. As the Generic--class can represent a black hole with two horizons or one horizon. First, we obtain the critical values of the magnetic charge and mass. Then, using the third--order WKB approximation, we can determine the dependence of the quasinormal modes with the parameters of the Generic--class. Finally, the transmission and reflection coefficients of the scattered wave in the third--order WKB approximation are calculated.

gr-qc↗

arXiv2022

Effects of quintessence on scattering and absorption sections of black holes

Basing on the ideas used by Kiselev, we study three black holes surrounded by quintessence and the effects of quintessence on the classical and semiclassical scattering cross-sections. In contrast, the absorption section is studied with the sinc approximation in the eikonal limit. For Schwarzschild, Reissner-Nordström and Bardeen black holes surrounded by quintessence, the values critical of charges and the normalization factor are obtained. We also described the horizons and the extremal condition of the black holes surrounded by quintessence. By setting for the quintessence state parameter in two the particular cases w=-2/3 and w=-1/2.

gr-qc↗

arXiv2021

Quasinormal modes of the Hayward black hole surrounded by quintessence: scalar, electromagnetic and gravitational perturbations

We study the quasi-normal modes for scalar, electromagnetic, and gravitational axial perturbations in the Hayward regular black hole surrounded by quintessence (HBH-$ω_q$). Using the third--order WKB approximation we can determine the dependence of the quasi--normal modes on the parameters of the regular black hole and the parameters on the test fields. We also determine the greybody factor, giving transmission and reflection coefficients of the scattered wave through the effective potentials in the WKB approximation using numerical analysis.

gr-qc↗

arXiv2021

Scattering and absorption sections of Schwarzschild-anti de Sitter with quintessence

In this paper, we study the scattering and absorption sections of the Schwarzschild--anti de Sitter black hole surrounded by quintessence. The critical values of the cosmological constant and the normalization factor are obtained. We describe the event horizons and the extremal condition of the black hole surrounded by quintessence. The effects of quintessence on the classical and semi--classical scattering cross--sections have been estimated. Also, the absorption section is studied with the sinc approximation in the eikonal limit. We consider the quintessence state parameter in the particular cases $ω=-2/3$ and $ω=-1/2$.

gr-qc↗

arXiv2021

Redshift of light emitted by particles orbiting a black hole immersed in a strong magnetic field

In this paper we analyze the frequency shifts of the light emitted by particles describing stable circular geodesics around a static black hole immersed in an external magnetic field of arbitrary strength. This system is represented by the Ernst solution of the Einstein-Maxwell equations. The presence of the magnetic field and its magnitude affects both the geodesics and the red-blueshifts of the light emitted by neutral or charged particles orbiting the black hole. When the magnetic field is turned off we recover the characteristic redshifts coming from particles orbiting a Schwarzschild black hole.

gr-qc↗

arXiv2021

Birefringence and QuasiNormal Modes of the Einstein-Euler-Heisenberg Black Hole

In this contribution we study the birefringence and the quasinormal modes (QNM) in the eikonal approximation, of the Einstein-Euler-Heisenberg black hole (EEH-BH) . The EEH-BH is an exact solution of the Einstein equations coupled to the Euler-Heisenberg nonlinear electrodynamics. It is well known that in the presence of strong electromagnetic fields light rays modify their trajectories and do follow the null geodesics of an effective metric as a result of the nonlinear interaction between light and the intense magnetic or electric background. In the Euler-Heisenberg theory the phenomenon of birefringence arises and then exist two possible light trajectories for polarized light in the vicinity of the EEH-BH. On the other hand, using the correspondence between the parameters of the null unstable geodesics and the quasinormal modes in the eikonal approximation. We determine these QNM for both, the electric and the magnetic EEH-BH and compare them with its linear counterpart, the Reissner-Nordström black hole, since there are two effective metrics, to each one corresponds one null geodesic that renders two possible QNM from the same compact object.

gr-qc↗

arXiv2020

Geodesics of Hayward black hole surrounded by quintessence

Basing on the ideas used by Kiselev, we study the Hayward black hole surrounded by quintessence. By setting for the quintessence state parameter at the special case of $ω=-\frac{2}{3}$, using the metric of the black hole surrounded by quintessence and the definition of the effective potential, we analyzed in detail the null geodesics for different energies. We also analyzed the horizons of the Hayward black hole surrounded by quintessence as well as the shadow of the black hole.

gr-qc↗

arXiv2020

Frequency Shifts of photons emitted from geodesics of nonlinear electromagnetic black holes

We analyzed the frequency shifts of photons emitted from massive particles that move in stable geodesics around black holes with non-linear electrodynamics. The motion of the photon is modified by an effective metric when the Einstein gravity is coupled with non-linear electrodynamics. The kinematic shifts for photons are modified by the magnetic and electric factors that make the difference between the linear and non-linear electrodynamics. As an illustration, we present the frequency shifts of the photons for black holes with non-linear electrodynamics, two magnetic black holes, and two electric black holes, the Bardeen and Bronnikov black holes for the magnetic charge and the Born-Infeld and Dymnikova black holes for electric charge. These frequency shifts are compared with their linear electromagnetic counterpart.

gr-qc↗

arXiv2020

Scattering and absorption sections of nonlinear electromagnetic black holes

The expression of the impact parameter, in the analysis for classical and semiclassical scattering cross sections for black holes, is obtained with nonlinear electrodynamics (NLED) while the absorption section is studied with the sinc approximation in the eikonal limit considering NLED. As an illustration, we calculate the classical and semiclassical scattering as well as the absorption sections for three black holes under NLED, the regular magnetic Bardeen and Bronnikov black holes and the singular Euler-Heisenberg black hole. All are compared with the sections of their linear electromagnetic counterpart, the Reissner-Nordstrom (RN) black hole. The comparison shows how NLED affects the sections as well as the variation with respect to the Reissner-Nordstrom sections, in some cases these variations are small.

gr-qc↗

arXiv2017

Corotating two-body system of identical Kerr sources

A binary system of identical corotating Kerr sources is studied after deriving the corresponding 3-parametric asymptotically flat exact solution. Both sources are apart from each other by means of a massless strut (conical singularity). In the context of black holes, the analytical functional form of each horizon σ is expressed in terms of arbitrary Komar physical parameters: mass M, angular momentum J (with parallel spin), and the coordinate distance R between the center of each horizon. Later on, all the thermodynamical properties related to the horizon are depicted by concise formulae. Finally, the extreme limit case is obtained as a 2-parametric subclass of Kinnersley-Chitre metric.

gr-qc↗