arXiv subjects

Moisés Bravo-Gaete

Publications and source records attributed to Moisés Bravo-Gaete.

18 recordsLinked to original sources

arXiv2026

Rotation and Anisotropic Scaling in Axionic Holographic Superconductors: AdS$_4$ versus Lifshitz$_5$

An outstanding question in holographic superconductivity is how rotation and non-relativistic scaling symmetries compete to modify the onset of condensation. We address this by comparing the probe superconductor sectors of two exact rotating axionic black holes: a four-dimensional asymptotically anti-de Sitter solution dressed by a non-minimally coupled scalar, and a five-dimensional asymptotically Lifshitz solution with $z \in (2,3)$. Writing both metrics in a common stationary form yields a master scalar equation in which rotation enters through the co-rotating potential $A_t-N^xA_x$. This equation explains why the temporal and spatial components of the probe gauge field cannot be treated independently. The numerical profiles reported in [1,2] indicate that the correlated deformation associated with rotation reduces the condensate amplitude in both backgrounds, whereas increasing the dynamical exponent at fixed $J$ enhances the Lifshitz condensate. Since the parameters $α$ and $J$ also modify the matter fields supporting the corresponding exact geometries, these trends should be interpreted as properties of complete correlated families rather than as universal effects of mechanical rotation alone.

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arXiv2026

Orbital stability, relativistic precession, and QPO constraints for constant-curvature black holes in $f(R)$ gravity

We analyze circular-orbit stability, epicyclic resonances, relativistic precession, and quasi-periodic-oscillation (QPO) constraints in the constant-curvature vacuum sector of metric $f(R)$ gravity. The Schwarzschild--(anti-)de~Sitter and Kerr--(anti-)de~Sitter backgrounds are characterized by curvature $R_0$ satisfying the algebraic trace equation. We derive stationary-coordinate-time orbital and epicyclic frequencies and determine stable timelike circular-orbit domains. Positive curvature confines stable motion between innermost and outermost stable circular orbits, which merge at a critical curvature, and permits two resonance radii for suitable frequency ratios. Negative curvature allows stable motion to arbitrarily large radii, with $Ω_θ/Ω_r\rightarrow1/2$, compared with unity in the asymptotically flat limit. We determine the $3{:}2$, $2{:}1$, and $3{:}1$ resonance branches and signed nodal precession, recovering the Lense--Thirring limit. We also evaluate angular-momentum-weighted rigid-flow precession and viscous alignment, with the outermost stable orbit bounding positive-curvature flows. A Bayesian Markov chain Monte Carlo analysis combining the simultaneous GRO J1655--40 QPO triplet with an independent dynamical-mass measurement yields $R_0M^2=-5.57^{+12.94}_{-16.15}\times10^{-4}$ at $68\%$ credibility, conditional on the geodesic relativistic-precession prescription and adopted time normalization. Kerr remains allowed, with negligible fit improvement from nonzero curvature. Doubling the mass uncertainty broadens the curvature interval by approximately $2.1$; removing the mass likelihood reveals an extended, prior-dependent degeneracy. This is therefore a joint QPO and dynamical-mass constraint, with no significant evidence for departure from Kerr.

gr-qc↗

arXiv2026

Multicritical points of gravitational solitons and a black hole in four dimensions

We present the first realization of multicritical points in four-dimensional general relativity, specifically within the context of Plebański nonlinear electrodynamics, using a polynomial structural function denoted as $\mathcal{H}(P)$. We show that this construction provides a systematic mechanism to engineer multicritical behavior in gravitational systems. By establishing an explicit mapping between matter theories expressed as power series in the Maxwell invariant $F$ and the Plebański formulation, we construct new families of electrically charged asymptotically anti-de Sitter black holes and magnetically charged solitons. In the grand-canonical ensemble, we analyze their thermodynamic properties and uncover a rich phase structure. We demonstrate that the soliton sector develops multiple swallowtail structures, signaling first-order phase transitions and allowing the coexistence of several magnetically charged solitons with a single electrically charged black hole. These configurations define multicritical points that generalize previously known triple points. We further show that the number of coexisting phases is controlled by the degree of the polynomial structural function, providing a direct link between the nonlinear electrodynamics couplings and the thermodynamic phase structure. In contrast, the black hole branch does not display swallowtail behavior, and it does not allow multiple electrically charged black holes to coexist with a magnetically charged soliton.

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arXiv2026

Novel five-dimensional rotating Lifshitz black holes with electric and axionic charges

In this work, we construct a new family of exact five-dimensional charged and rotating asymptotically Lifshitz black holes. The spacetime solves Einstein equations coupled to a dilaton, two Abelian gauge fields, and axionic scalars supplemented by two generalized Chern-Simons terms. This configuration is characterized by a range of the free dynamical exponent $z$ and possesses nontrivial thermodynamical parameters, where we verify the first law of black hole thermodynamics and derive the corresponding Smarr relation. As an application of this new gravitational background, we then investigate a holographic superconductor in the rotating Lifshitz background. We study the condensation of the scalar operator and the AC conductivity of the dual system. These results show that increasing the rotation parameter suppresses the condensate and weakens the superconducting phase, while increasing the dynamical critical exponent enhances the superconducting order. To the best of our knowledge, these solutions provide the first explicit family of five-dimensional rotating Lifshitz black holes supported simultaneously by electric and axionic charges.

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arXiv2026

A new rotating axionic AdS$_4$ black hole dressed with a scalar field

This paper presents a new four-dimensional axionically charged rotating black hole with a scalar field, which is defined by a structural function coupling the axionic field and a scalar potential. This configuration is characterized by an integration constant and two constant parameters. The thermodynamic quantities are obtained via the Euclidean procedure, where the validity of the first law of thermodynamics is ensured. These results indicate that the rotating configuration provides a useful framework for exploring holographic superconductors, where the angular constant parameter plays a central role.

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arXiv2026

Periodic orbits and gravitational waveforms of spinning particles in nonlocal Gravity

In this paper, we investigate the dynamics and gravitational-wave signatures of periodic orbits of spinning test particles moving in the equatorial plane around static, spherically symmetric black holes within the framework of Deser-Woodard nonlocal gravity. Based on the Mathisson-Papapetrou-Dixon equations, combined with the Tulczyjew spin supplementary condition, we derive the orbital dynamic equations for spinning particles moving in the equatorial plane and impose a timelike constraint to exclude unphysical superluminal trajectories. By comparing with the classical Schwarzschild black hole, we systematically analyze the effects of the nonlocal gravitational parameters $ζ$ and $b$ on the effective potential governing the radial motion of particles and the innermost stable circular orbit. In addition, gravitational waveforms exhibit significant phase differences: an increase in $ζ$ induces a phase delay, whereas an increase in $b$ results in a phase advance. A one-year simulation of the orbital evolution of an extreme mass ratio inspiral demonstrates that when $b=2$ and $ζ\approx10^{-6}$, the mismatch between the gravitational waveforms predicted for the nonlocal gravity black hole and those for the Schwarzschild black hole reaches the distinguishable threshold ($\mathcal{M}=0.0125$), providing a basis for observational discrimination between general relativity and nonlocal gravity.

gr-qc↗

arXiv2026

Transport coefficients of charged Gauss-Bonnet black holes with arbitrary topology

In this study, we present a novel family of exact black hole solutions constructed in the context of five-dimensional Gauss-Bonnet gravity. These solutions add a non-linear charge to the Bañados-Teitelboim-Zanelli-like configurations known to exist with arbitrary Thurston horizon geometry. We establish constraints on the parameter space defining physically viable black holes, aligning with the standard energy conditions. An explicit proof of the first law of thermodynamics within our scenario is provided. We also employ holographic techniques to characterize the DC conductivities for the distinct horizon geometries, identifying a critical temperature indicative of phase transitions and exploring pertinent limits.

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arXiv2025

Mass inflation and strong cosmic censorship conjecture in the covariant quantum black hole

Recently, two types of solutions to the long-standing issue of general covariance in canonical quantum gravity have been proposed. From the above, a fundamental question arises: which solution is superior? Considering one type of solution with a Cauchy horizon, in the present letter, we explore whether it exhibits properties similar to those of the Reissner-Nordström black hole. Due to its geometric similarity, application of the generalized Dray-'t Hooft-Redmond relation reveals evidence of mass inflation, indicating that the Cauchy horizon is unstable. While this is consistent with the Strong Cosmic Censorship conjecture, it suggests that it does not represent a regular black hole. Furthermore, we extend the metric to include a cosmological constant and study the validity of the Strong Cosmic Censorship conjecture for the quantum black hole in de Sitter spacetime. After taking into account the reasonable ranges of parameters for the quantum black hole, we find that the Strong Cosmic Censorship Conjecture holds.

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arXiv2024

Magnetized AdS/BCFT Correspondence in Horndeski Gravity

This work examines the thermodynamics and hydrodynamics behaviors of a five-dimensional black hole under the influence of an external magnetic field. The solution is the gravity dual to the Anti-de Sitter/Boundary Conformal Field Theory correspondence, enabling the study of properties within an anisotropic fluid framework. Utilizing holographic renormalization, we compute the free energy and the holographic stress tensor residing on the boundary denoted as $Q$. Within the fluid/gravity correspondence framework, we have a class of boundary extensions in $Q$, where the stress-energy tensor describes a magnetizing conformal fluid. We discuss the characteristics of this special solution as well as its thermodynamic properties, including the bulk and shear viscosity, the square of the speed of sound, as well as the anisotropic effects induced by the magnetic field in the magnetized conformal plasma.

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arXiv2024

Quasinormal modes, greybody factors and thermodynamics of four dimensional AdS black holes in Critical Gravity

In the present work, considering critical gravity as a gravity model, an electrically charged topological Anti-de Sitter black hole with a matter source characterized by a nonlinear electrodynamics framework is obtained. This configuration is defined by an integration constant, three key structural constants, and a constant that represents the topology of the event horizon. Additionally, based on the Wald formalism, we probe that this configuration enjoys non-trivial thermodynamic quantities, establishing the corresponding first law of black hole thermodynamics, as well as local stability under thermal and electrical fluctuations. Additionally, via the Gibbs free energy we note that the topology of the base manifold allows us to compare this charged configuration with respect to the thermal AdS space-time, allowing us to obtain a first-order phase transition. The quasinormal modes and the greybody factor are also calculated by considering the spherical situation. We found that the quasinormal modes exhibit a straightforward change for variations of one of the structural constants.

gr-qc↗

arXiv2023

AdS/BCFT correspondence and Horndeski gravity in the presence of gauge fields: holographic paramagnetism/ferromagnetism phase transition

This paper presents a dual gravity model for a (2+1)-dimensional system with a limit on finite charge density and temperature, which will be used to study the properties of the holographic phase transition to paramagnetism-ferromagnetism in the presence of Horndeski gravity terms. In our model, the non-zero charge density is supported by a magnetic field. As a result, the radius $ρ/B$ indicates a localized condensate, as we increase the Horndeski gravity parameter, that is represented by $γ$. Furthermore, such condensate shows quantum Hall-type behavior. This radius is also inversely related to the total action coefficients of our model. It was observed that increasing the Horndeski parameter decreases the critical temperature of the holographic model and leads to the harder formation of the magnetic moment at the bottom of the black hole. However, when removing the magnetic field, the ferromagnetic material presents a disorder of its magnetic moments, which is observed through the entropy of the system. We also found that at low temperatures, spontaneous magnetization and ferromagnetic phase transition.

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arXiv2023

Exploring the shear viscosity in four-dimensional planar black holes beyond General Relativity

The well known shear viscosity to entropy density ratio ($η/s$) cannot be computed when the black hole space-time has zero thermodynamic entropy. This is the case, for example, when General Relativity in four dimensions is complemented with Critical Gravity, or in particular scenarios within the Four-dimensional-scalar-Gauss-Bonnet theories. Recently, it has been shown that the zero entropy situation can be overcome in these examples by introducing suitable matter fields. With this at hand, in this paper we analyze each case and the impact of these extra sources in the ratio, in terms of their new parameters. We find that, while the $η/s$ ratio remains constant and insensitive in the former, this is not the case for the latter. To perform the calculations, we construct a Noether charge using a space-like Killing vector. The accuracy of the aforementioned findings is supported by the Kubo formalism.

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arXiv2022

Shear viscosity from black holes in generalized scalar-tensor theories in arbitrary dimensions

In higher dimensions, we study Degenerate-Higher-Order-Scalar-Tensor theories and we derive solutions that resemble the Schwarzschild Anti-de Sitter black holes. We compute their thermodynamic quantities following the Wald formalism, satisfying the First Law of Thermodynamics and a higher dimensional Smarr relation. Constructing a Noether charge with a suitable choice of a space-like Killing vector, we obtain the shear viscosity of the non-gravitational dual field theory, where for a suitable choice of the couplings functions, the Kovtun-Son-Starinets bound is violated. These results are corroborated by the calculation of the Green's functions following the Kubo formalism.

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arXiv2022

Non-linear charged planar black holes in four-dimensional Scalar-Gauss-Bonnet theories

In this work, we consider the recently proposed well-defined theory that permits a healthy $D\to 4$ limit of the Einstein-Gauss-Bonnet combination, which requires the addition of a scalar degree of freedom. We continue the construction of exact, hairy black hole solutions in this theory in the presence of matter sources, by considering a nonlinear electrodynamics source, constructed through the Plebański tensor and a precise structural function $\mathcal{H}(P)$. Computing the thermodynamic quantities with the Wald formalism, we identify a region in parameter space where the hairy black holes posses well-defined, non-vanishing, finite thermodynamic quantities, in spite of the relaxed asymptotic approach to planar AdS. We test its local stability under thermal and electrical fluctuations and we also show that a Smarr relation is satisfied for these black hole configurations.

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arXiv2022

Thermodynamics of non-linearly charged Anti-de Sitter black holes in four-dimensional Critical Gravity

In this work, we provide new examples of Anti-de Sitter black holes with a planar base manifold in four-dimensional Critical Gravity by considering nonlinear electrodynamics as a matter source. We find a general solution characterized by the presence of only one integration constant where, for a suitable election of coupling constants, we can show the existence of one or more horizons. Additionally, we compute its non-null thermodynamical quantities through a variety of techniques, testing the validity of the first law of thermodynamics as well as a Smarr formula. Finally, we analyze the local thermodynamical stability of the solutions. To our knowledge, these charged configurations are the first example with Critical Gravity where their thermodynamical quantities are not zero.

gr-qc↗

arXiv2022

Complexity of four-dimensional hairy Anti-de-Sitter black holes with a rotating string and shear viscosity in generalized scalar-tensor theories

In four dimensions, we consider a generalized scalar-tensor theory where the coupling functions only depend on the kinetic term of the scalar field. For this model, we obtain a set of hairy Anti-de-Sitter black hole solutions, allowing us to calculate the computational complexity, according to the Complexity equals Action conjecture. To perform this, the system contains a particle moving on the boundary, corresponding to the insertion of a fundamental string in the bulk. The effect string is given by the Nambu-Goto term, analyzing the time development of this system. Together with the above, we calculate the shear viscosity, where the viscosity/entropy density ratio can violate the Kovtun-Son-Starinets bound for a suitable choice of coupling functions.

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arXiv2022

Planar black holes configurations and shear viscosity in arbitrary dimensions with shift and reflection symmetric scalar-tensor theories

In higher dimensions, we explore planar hairy black hole configurations for a special subclass of the Horndeski theory, defined by two coupling functions depending on the kinetic term and enjoying shift symmetry and reflection symmetry. For this analysis, we derive a set of new solutions, given by time-dependent as well as time independent scalar field configurations. Additionally, we calculate their thermodynamic quantities by using Wald formalism, satisfying the First Law of Thermodynamics as well as a Smarr relation. Together with the above, the Wald procedure allows us to compute the shear viscosity, showing that for a suitable choice of the coupling functions the Kovtun-Son-Starinets bound is violated.

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arXiv2019

Microscopic entropy of higher-dimensional nonminimally dressed Lifshitz black holes

In arbitrary dimension, we consider a theory described by the most general quadratic curvature corrections of Einstein gravity together with a self-interacting nonminimally coupled scalar field. This theory is shown to admit five different families of Lifshitz black holes dressed with a nontrivial scalar field. The entropy of these configurations is microscopically computed by means of a higher-dimensional anisotropic Cardy-like formula where the role of the ground state is played by the soliton obtained through a double analytic continuation. This involves to calculate the correct expressions for the masses of the higher-dimensional Lifshitz black hole as well as their corresponding soliton. The robustness of this Cardy-like formula is checked by showing that the microscopic entropy is in perfect agreement with the gravitational Wald entropy. Consequently, the calculated global charges are compatible with the first law of thermodynamics. We also verify that all the configurations satisfy an anisotropic higher-dimensional version of the Smarr formula.

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