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Ángel Rincón

Publications and source records attributed to Ángel Rincón.

At least 37 records · Page 2Linked to original sources
arXiv2022

Quasinormal modes of massive scalar fields in four-dimensional wormholes: anomalous decay rate

In this work we consider a Generalized Bronnikov-Ellis wormhole and the tideless Morris-Thorne wormhole and we study the propagation of massive scalar fields. We calculate the quasinormal frequencies using the WKB method and the pseudospectal Chebyshev method and we show the presence of an anomalous decay rate for the quasinormal modes in the Generalized Bronnikov-Ellis wormhole. However, such anomalous behaviour is avoided for the fundamental mode in the Morris-Thorne wormhole background.

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arXiv2022

Binary X-ray sources in massive Brans-Dicke gravity

This study focuses on the X-ray emission of low-mass black hole binaries in massive Brans-Dicke gravity. First, we compute the accretion disk adopting the well-known Shakura-Sunyaev model for an optically thick, cool, and geometrically thin disk. Moreover, we assume that the gravitational field generated by the stellar-mass black hole is an analogue of the Schwarzschild space-time of Einstein's theory in massive Brans-Dicke gravity. We compute the most relevant quantities of interest, i.e., i) the radial velocity, ii) the energy and surface density, and iii) the pressure as a function entirely of the radial coordinate. We also compute the soft spectral component of the X-ray emission produced by the disk. Furthermore, we investigate in detail how the mass of the scalar field modifies the properties of the binary as described by the more standard Schwarzschild solution.

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arXiv2021

Slowly rotating dark energy stars

We study isotropic and slowly-rotating stars made of dark energy adopting the extended Chaplygin equation-of-state. We compute the moment of inertia as a function of the mass of the stars, both for rotating and non-rotating objects. The solution for the non-diagonal metric component as a function of the radial coordinate for three different star masses is shown as well. We find that i) the moment of inertia increases with the mass of the star, ii) in the case of non-rotating objects the moment of inertia grows faster, and iii) the curve corresponding to rotation lies below the one corresponding to non-rotating stars.

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arXiv2021

Superradiant instability and charged scalar quasinormal modes for $2+1$-dimensional Coulomb-like AdS black holes from nonlinear electrodynamics

We study the propagation of charged scalar fields in the background of $2+1$-dimensional Coulomb-like AdS black holes, and we show that such propagation is unstable under Dirichlet boundary conditions. However, all the unstable modes are superradiant and all the stable modes are non-superradiant, according with the superradiant condition. Mainly, we show that when the scalar field is charged the quasinormal frecuencies (QNFs) are always complex, contrary to the uncharged case, where for small values of the black hole charge the complex QNFs are dominant, while that for bigger values of the black hole charge the purely imaginary QNFs are dominant.

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arXiv2021

Growth of structures and redshift-space distortion data in scale-dependent gravity

This study is devoted to the implications of scale-dependent gravity in Cosmology. Redshift-space distortion data indicate that there is a tension between $Λ$CDM and available observations as far as the value of the rms density fluctuation, $σ_8$, is concerned. It has been pointed out that this tension may be alleviated in alternative theories in which gravity is weaker at red-shift $z \sim 1$. We study the evolution of density perturbations for non-relativistic matter on top of a spatially flat FLRW Universe, and we compute the combination $A=f σ_8$ in the framework of scale-dependent gravity, where both Newton's constant and the cosmological constant are allowed to vary with time. Upon comparison between available observational data (supernovae data as well as redshift-space distortion data) and theoretical predictions of the model, we determine the numerical value of $σ_8$ that best fits the data.

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arXiv2020

Greybody factor and quasinormal modes of Regular Black Holes

In this work, we investigate the quasinormal frequencies of a class of regular black hole solutions which generalize Bardeen and Hayward spacetimes. In particular, we analyze scalar, vector and gravitational perturbations of the black hole both with the semianalytic WKB method and their time-domain profiles. We analyze in detail the behavior of the spectrum depending on the parameter $p/q$ of the black hole, the quantum number of angular momentum and the $s$ number. In addition, we compare our results with the classical solution valid for $p = q = 1$.

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arXiv2020

Durgapal IV model in light of the minimal geometric deformation approach

The present article is devoted to the study of local anisotropies effects on the Durgapal's fourth model in the context of gravitational decoupling via the Minimal Geometric Deformation approach. To do it, the most general equation of state relating the components of the $θ$--sector is imposed to obtain the decoupler function $f(r)$. In addition, certain properties of the obtained solution are investigated, such as the behavior of the salient material content threading the stellar interior, causality and energy conditions, hydrostatic balance through modified Tolman--Oppenheimer--Volkoff conservation equation and stability mechanism against local anisotropies by means of adiabatic index, sound velocity of the pressure waves, convection factor and Harrison--Zeldovich--Novikov procedure, in order to check if the model is physically admissible or not. Regarding the stability analysis, it is found that the model presents unstable regions when the sound speed of the pressure waves and convection factor are used in distinction with what happens in the adiabatic index and Harrison--Zeldovich--Novikov case. To produce a more realistic picture the numerical data for some known compact objects was placed and different values of the parameter $α$ were considered to compare with the GR case ı.e, $α=0$.

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arXiv2020

Interior solutions of relativistic stars in the scale-dependent scenario

We study relativistic stars in the scale-dependent scenario, which is one of the approaches to quantum gravity, and where Newton's constant is promoted to a scale-dependent quantity. First, the generalized structure equations are derived here for the first time. Then they are integrated numerically assuming a linear equation-of-state in the simplest MIT bag model for quark matter. We compute the radius, the mass and the compactness of strange quarks stars, and we show that the energy conditions are fulfilled.

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arXiv2020

Black hole shadow of a rotating scale--dependent black hole

In this work, starting from a spherically symmetric scale--dependent black hole, a rotating solution is obtained by following the Newman--Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we get and discuss the shape of its shadow.

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arXiv2019

Quasinormal modes of five-dimensional black holes in non-commutative geometry

We compute the spectrum of quasinormal frequencies of five-dimensional black holes obtained in noncommutative geometry. In particular, we study scalar perturbations of a massive scalar field adopting the 6th order WKB approximation. We investigate in detail the impact of the mass of the scalar field, the angular degree and the overtone number on the spectrum. All modes are found to be stable.

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arXiv2019

Relativistic strange quark stars in Lovelock gravity

We study relativistic non-rotating stars in the framework of Lovelock gravity. In particular, we consider the Gauss-Bonnet term in a five-dimensional spacetime, and we investigate the impact of the Gauss-Bonnet parameter on properties of the stars, both isotropic and anisotropic. For matter inside the star, we assume a relativistic gas of de-confined massless quarks. We integrate the modified Tolman-Oppenheimer-Volkoff equations numerically, and we obtain the mass-to-radius profile, the compactness of the star as well as the gravitational red-shift for several values of the Gauss-Bonnet parameter. The maximum star mass and radius are also reported.

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arXiv2019

Anisotropic strange quark stars with a non-linear equation-of-state

We obtain an exact analytical solution to Einstein's field equations assuming a non-linear equation-of-state and a particular mass function. Our solution describes the interior of anisotropic color flavor locked strange quark stars. All energy conditions are fulfilled, and therefore the solution obtained here is a realistic solution within General Relativity. The mass-to-radius profile is obtained, and the compactness of the star is computed.

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arXiv2019

Quasinormal modes of regular black holes with non linear-Electrodynamical sources

We compute the spectrum of quasinormal frequencies of regular black holes obtained in the presence of Non-Linear Electrodynamics. In particular, we perturb the black hole with a minimally coupled massive scalar field, and we study the corresponding perturbations adopting the 6th order WKB approximation. We analyze in detail the impact on the spectrum of the charge of the black hole, the quantum number of angular momentum and the overtone number. All modes are found to be stable. Finally, a comparison with other charged black holes is made, and an analytical expression for the quasinormal spectrum in the eikonal limit is provided.

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arXiv2019

Photons trajectories on a first order scale-dependent static BTZ black hole

In this paper we study the motion of massless particles on a static BTZ black hole background in the context of scale-dependent gravity, which is characterized by the running parameter $ε$. Thus, by using standard methods we obtain the equation of motions and then analytic solutions are found. The relevant non-trivial differences appear when we compare our solution against the classical counterpart.

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arXiv2019

The Sagnac effect on a scale-dependent rotating BTZ black hole background

In this paper we investigate the Sagnac effect by calculating the difference in travel time and phase shift observed for photon beams counter--propagating in a rotating interferometer on a BTZ black hole solution in the context of scale-dependent gravity, which describes the field around a massive static and rotating object in $2+1$ gravity.

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arXiv2019

Scale-dependent planar Anti-de Sitter black hole

In this work, we investigate four-dimensional planar black hole solutions in anti-de Sitter spacetimes in light of the so-called scale-dependent scenario. To obtain this new family of solutions, the classical couplings of the theory, i.e., the gravitational coupling and the cosmological constant, are not taken to be fixed values anymore. Thus, those classical parameters evolve to functions which change along the "height" coordinate, z. The effective Einstein field equations are solved, and the results are analyzed and compared with the classical counterpart. Finally, some thermodynamic properties of the presented scale--dependent black hole are investigated.

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arXiv2018

Greybody factors and quasinormal modes for a nonminimally coupled scalar field in a cloud of strings in (2+1)-dimensional background

We study the propagation of a probe massless nonminimally coupled scalar field in a fixed gravitational background of a cloud of strings in (2+1) dimensions. We obtain exact analytical expressions for the reflection coefficient, the absorption cross section, the decay rate as well as the quasinormal frequencies. The impact of the nonminimal coupling is investigated in detail. Our results show that Universality is not respected in general, and that scalar perturbations are stable.

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