arXiv subjects

Ulises Hernandez-Vera

Publications and source records attributed to Ulises Hernandez-Vera.

6 recordsLinked to original sources

arXiv2026

Rotating black holes with primary hair in five-dimensional generalized Proca theory

This work presents a new class of exact analytic rotating black hole solutions within five-dimensional generalized Proca theories. Through a Kerr-Schild ansatz where the Proca field is set along a null geodesic congruence, the non-linear field equations reduce to a consistent set of three master equations. This geometric configuration ensures that the vector field remains light-like on-shell, effectively restricting the theory's functional couplings to discrete constants and allowing for a fully analytic treatment. The resulting solutions, incorporating a cosmological constant and two independent angular momenta, exhibit primary hair given by an arbitrary function of the non-Killing angular coordinate. We identify several solution branches defined by specific algebraic relations between the Proca coupling constants, providing a significant generalization of the Myers-Perry family. Notably, the metric retains a Kerr-Schild form identical to the Myers-Perry representation, with an additional contribution constructed from the tensor product of the Proca one-form with itself.

gr-qc↗

arXiv2025

ModMax Electrodynamics and Holographic Magnetotransport

We study magnetotransport in a holographic model where ModMax nonlinear electrodynamics is coupled to Einstein anti--de Sitter gravity. To incorporate momentum relaxation, we introduce spatially linear free scalar fields that break translational symmetry, resulting in an anisotropic medium. Using linear response theory, we compute the DC conductivity matrix in the presence of an external magnetic field, expressing the conductivities in terms of horizon data. Our results demonstrate how the nonlinear ModMax parameter modifies charge transport, particularly influencing the Hall angle and Nernst signal. The nonlinear corrections introduce distinct deviations in both longitudinal and Hall conductivities while preserving the characteristic temperature scaling of strange metals, offering new insights into strongly coupled systems with nonlinear electromagnetic interactions. Notably, the Nernst signal reproduces that of high-$T_c$ cuprate superconductors showing a superconducting dome and a normal phase, with the ModMax deformation parameter tuning critical and onset temperatures. In the strongly nonlinear regime, we find evidence of an exotic state dominated by quasiparticle excitations in the dual material.

hep-th↗

arXiv2025

Thermodynamics of four-dimensional regular black holes with an infinite tower of regularized curvature corrections

We study the thermodynamics of a class of four-dimensional black hole solutions arising from the compactification of a higher-curvature gravity theory featuring an infinite tower of Lovelock-type invariants. For planar horizons, we identify two distinct branches: a regular black hole supported by a nontrivial scalar field and a non-regular general relativity (GR) solution with a trivial scalar profile. Despite their differing geometries, both branches share the same free energy at fixed temperature, revealing a thermodynamic degeneracy naturally linked to the enhanced symmetry and scale invariance of the planar base manifold. In the case of a spherical horizon, even if the scalarized branch is not obtained in closed form, one can see that the degeneracy persists in the absence of the quadratic curvature contribution. On the other hand, if this quadratic term is taken into account, the regular solution may be thermodynamically favored (or not) over the Schwarzschild-AdS solution depending on the values of the coupling constants of the theory.

gr-qc↗

arXiv2025

The lack of influence of the scalar hair on the DC conductivity

Recently obtained black hole solutions within the framework of beyond-Horndeski theories, which have the advantage of featuring primary hair, are generalized in the presence of two axionic fields. In order to induce a momentum dissipation, the axionic field solutions are homogeneously distributed along the horizon coordinates of the planar base manifold. We show that, despite the explicit dependence of the scalar field and the metric on the primary hair, this latter does not directly affect the calculation of transport properties. Its influence is indirect, modifying the horizon location, but the transport properties themselves do not explicitly depend on the hair parameter. We take a step further and show that even within a more general class of beyond-Horndeski theories, where the scalar field depends linearly on the hair parameter, the scalar hair still has no direct impact on the DC conductivity. This result underscores the robustness of our earlier findings, and seem to confirm that the transport properties remain unaffected by the explicit presence of the hair parameter.

hep-th↗

arXiv2023

Endorsing black holes with beyond Horndeski primary hair: An exact solution framework for scalarizing in every dimension

This work outlines a straightforward mechanism for endorsing primary hair into Schwarzschild black holes, resulting in a unique modification within the framework of a special scalar-tensor theory, the so-called beyond Horndeski type. The derived solutions are exact, showcase primary hair with an everywhere regular scalar field profile, and continuously connect with the vacuum geometry. Initially devised to introduce primary hair in spherically symmetric solutions within General Relativity in any dimension, our investigation also explores the conditions under which spherically symmetric black holes in alternative gravitational theories become amenable to the endorsement of primary hair through a similar pattern. As a preliminary exploration, we embark on the process of endorsing primary hair to the Reissner-Nordström black hole. Subsequently, we extend our analysis to encompass spherically symmetric solutions within Lovelock and cubic quasitopological gravity theories.

hep-th↗

arXiv2023

From static to Vaidya solutions in scalar tensor theories

We consider some classes of Horndeski theories in four dimensions for which a certain combination of the Einstein equations within a spherical ansatz splits into two distinct branches. Recently, for these theories, some integrability and compatibility conditions have been established which have made it possible to obtain black hole solutions depending on a single integration constant identified as the mass. Here, we will show that these compatibility conditions can be generalized to accommodate a time dependence by promoting the constant mass to an arbitrary function of the retarded (advanced) time. As a direct consequence, we prove that all the static black hole solutions can be naturally promoted to non static Vaidya-like solutions. We extend this study in arbitrary higher dimensions where the pure gravity part is now described by the Lovelock theory and, where the scalar field action enjoyed the conformal invariance. For these theories, the splitting in two branches is also effective, and we show that their known static black hole solutions can as well be promoted to Vaidya-like solutions.

hep-th↗