arXiv subjects

M. Sabido

Publications and source records attributed to M. Sabido.

At least 19 recordsLinked to original sources

arXiv2026

On entropic cosmology, late time acceleration and the quantum bounce

In this work, we present a unified entropic description of the quantum bounce that is present in Loop Quantum Cosmology (LQG) and dark energy that drives the late time acceleration of the Universe. By considering a minimal area $A_0$ for the Universe and a modified entropy area constructed as the sum of $S_Q$, $S_{BH}$ and $S_{DE}$, we derive the Friedmann equations. We show that in the limit $A\sim A_0$, there is a critical density that generates the quantum bounce and depends on the minimal area. Moreover, in the limit $A\gg A_0$ (large Universe) the late time dynamics gives an accelerating scale factor. Therefore, we can argue an entropic origin for the quantum bounce and dark energy.

gr-qc↗

arXiv2026

Comments on deformed phase-space cosmology, SUSY and black holes

This paper presents the construction of the supersymmetric (SUSY) deformed version of the time dependent metric that describes the interior of the Schwarzschild BH. First, the noncommutative bosonic model is constructed by inducing the deformation in the minisuperspace coordinates and the associated canonical momentum. Following the methods of SUSY quantum mechanics, the supercharges of the deformed models are constructed and the deformed SUSY Wheeler-DeWitt equation is obtained. The classical dynamics are also obtained using the WKB approximation, we find the classical solutions and the conditions to satisfy the Hamiltonian constraint for both the SUSY and bosonic cases. Finally, the effects of the deformation in the context of deformed phase space cosmology and black holes are discussed.

hep-th↗

arXiv2026

Static Black Holes and Iyer-Wald Entropy in $f(\mathcal{R},\mathcal{K})$ Gravity

We investigate static, spherically symmetric black hole solutions in a class of higher-curvature gravitational theories described by a Lagrangian that depends on the Ricci and Kretschmann scalars. The modified Einstein equations contain higher-order curvature terms. We develop a perturbative scheme to look for a black hole solution that deviates parametrically from the Schwarzschild geometry. We obtain first-order corrections to the metric by solving the resulting coupled differential equations. The corresponding Iyer--Wald entropy is then evaluated consistently to first order in the perturbative coupling. We show that the higher-curvature contribution gives rise to a power-law correction to the Bekenstein--Hawking entropy.

gr-qc↗

arXiv2026

On Deformed Phase Space Black Holes

We revisit the Schwarzschild black hole in the context of noncommutative phase space. By mapping the horizon area operator into a two-dimensional harmonic oscillator structure, we derive the modifications induced by phase space noncommutativity. The formalism is developed using the generalized Bopp shift on the canonical coordinates and momenta. We computed the modified area spectrum, black hole mass levels, transition frequencies, Hawking temperature, and entropy, highlighting the physical implications of the deformation parameters $\theta$ and $\eta$ on the thermodynamical properties of the deformed black hole. Finally, we conjecture a connection between the noncommutative contribution to the entropy and Barrow's entropy.

gr-qc↗

arXiv2026

Generalized ModMax and the Early Universe

In this work, we study a cosmological model driven by Generalized ModMax nonlinear electrodynamics. We find that, with an appropriate choice of the theory's parameters, the universe's initial singularity can be avoided. Moreover, we also find that this model has an inflationary epoch that is consistent with the current values for $N$, $n_s$ and $r$. Therefore, using Generalized ModMax, we can construct a non singular Universe with an inflationary epoch.

gr-qc↗

arXiv2025

S-Duality and Categorical Gauge Theory

In this work, we revisit abelian S-duality in the context of higher gauge theory. By using a specific crossed module a set of transformations arise, which are known as the "thin" and "fat" transformations. The "fat" transformations are the ones introduced by hand to construct the S-dual theory. By utilizing crossed modules and higher gauge theory, we arrive at transformations referred to by some as "third-type transformations", giving these transformations a geometric interpretation, as transformations of a local 2-connection in a 2-principal bundle. This approach opens a new perspective to understand S-duality in non-abelian gauge theories through higher gauge theory.

hep-th↗

arXiv2025

On planetary orbits, ungravity and entropic gravity

In previous works, entropic gravity and ungravity have been considered as possible solutions to the dark energy and dark matter problems. To test the viability of these models, modifications to planetary orbits are calculated for ungravity and different models of entropic gravity. Using the gravitational sector of unparticles, an equation for the contribution to the effect of orbital precession is obtained. We conclude that the estimated values for the ungravity parameters from planetary orbits are inconsistent with the values needed for the cosmological constant. The same ideas are explored for entropic gravity arising from a modified entropy--area relationship.

gr-qc↗

arXiv2025

Chern-Simons Inspired Massive Gravity

In this work we propose a new 2+1 theory of gravity. We start with a modification of Chern-Simons 2+1 gravity. By introducing a vector field $\Phi$ to the usual composition of the vierbein and connection, we derive a new action that includes the Einstein-Hilbert term, a cosmological constant and a polynomial term for the vector field. This allows us to write a Chern-Simons inspired Massive Gravity. After solving the polynomial function, the action can be rewritten as a Born-Infeld type action. Moreover, we show that the second order expansion of this action is equivalent to New Massive Gravity. We explore solutions to the theory and show that it has a BTZ solution with an effective cosmological constant in terms of the parameters of the theory, global Lifshitz space-times as well as regular Lifshitz black holes, and asymptotically flat black holes.

hep-th↗

arXiv2024

Observational constraints on entropic cosmology

In this work, we derive a generalized modified Friedmann equation based on an entropy-area relation that incorporates established modifications, such as volumetric, linear, and logarithmic terms, in addition to novel entropic modifications that might yield to relevant cosmological implications at different stages of the evolution of the Universe. Some of these modifications are capable of mimicking the effects of dark energy and describing the current state of accelerated expansion of the Universe. We study particular cases of the generalized Friedmann equation and constrain the free parameters using observational datasets, including Hubble parameter measurements, baryon acoustic oscillations, and strong lensing systems. Our findings indicate that the proposed models align well with current observational data, particularly in low-redshift regimes; furthermore, these models are compatible with the value of $H_0$ obtained by the SH0ES program.

gr-qc↗

arXiv2023

Phase space deformations in SUSY cosmology

In this paper we propose a SUSY generalization for deformed phase-space cosmology. In particular, scalar field and phantom cosmology are studied. We construct the supercharges of the models and the SUSY Wheeler-DeWitt equation. We also construct and derive the classical dynamics using the WKB approximation.

gr-qc↗

arXiv2023

On the Generalized Uncertainty Principle and Cosmology

In this work we study the effects of the generalized uncertainty principle (GUP) in cosmology. We start with the Friedmann-Robertson-Walker (FRW) model endowed with a scalar field. After introducing the GUP modification to the model, we solve for the quantum and classical cases. Finally we find the GUP modified Friedmann equations.

gr-qc↗

arXiv2023

Cosmic acceleration in entropic cosmology

In this paper we study the viability of an entropic cosmological model. The effects of entropic gravity are derived from a modified entropy-area relationship with a volumetric entropy term. This model describes a late time limit cosmic acceleration, whose origin is related to a volumetric term in the entropy. Moreover, we analyze the phenomenological implications of the entropic model using the Supernovae Pantheon compilation and the observational Hubble parameter data to find consistency with cosmological observations. Finally, we show the equivalence between the entropic model and a brane world cosmological model, by means of an effective geometrical construction.

gr-qc↗

arXiv2023

Vector-tensor gravity from a broken gauge symmetry

In this paper we present a Yang-Mills type gauge theory of vector-tensor gravity, where the tetrad, the spin connection and vector field are identified with components of the gauge field. This setup leads to a theory that is contained in Generalized Proca theories. We solve for static and spherically symmetric space-time and show that there are two branches of solutions, one where the metric is asymptotically Schwarzschild even though there is a cosmological constant in the action, and another one where the metric is asymptotically (anti-)de Sitter. Also, we study the effect of the vector field on homogeneous and isotropic spacetimes, finding that it contributes to the accelerated expansion of the metric.

gr-qc↗

arXiv2022

Noncommutative SUSY Black Holes

In this paper we propose a generalization to the Schwarzschild metric and define noncommutative SUSY black holes. We introduce the noncommutative deformation to the minisuperspace variables and derive the noncommutative supersymmetric (SUSY) Wheeler-DeWitt (WDW) equation for the Schwarzschild black hole. We calculate the metric and find that the singularities are not removed.

hep-th↗

arXiv2022

On superstatistics and black hole quasinormal modes

It is known that using Boltzmann-Gibbs statistics, Bekenstein-Hawking entropy $S_{HB}$, and the quasinormal modes of black holes, one finds that the lowest value of spin is $j_{min}=1$. In this paper, we determine $j_{min}$, using non-extensive entropies that depend only on the probability (known as Obregon's entropies and have been derived from superstatistics). We also calculate $j_{min}$ for a set of non-extensive entropies that have free parameters and are written in terms of $S_{BH}$. We find that $j_{min}$ depends on the area and the non-extensive parameter. For the non-extensive entropies that only depend on the probability, we find that the modification is only present for micro black holes. For classical black holes the results are the same as for the Boltzmann-Gibbs statistics.

gr-qc↗

arXiv2022

Cosmology and Non-additive Entropy

Non-additive entropies have been proposed as alternatives to understanding the thermodynamics of Black Holes. Moreover, it has been suggested that the difficulties of quantization of gravity are an indication that gravity is an emergent phenomenon, and therefore an entropic formulation is warranted. In this work, we explore cosmologies that come from non-additive entropies. We focus our study on the cosmologies derived from entropies in superstatistics.

gr-qc↗

arXiv2021

On Planetary Orbits in Entropic Gravity

Starting with an entropy that includes volumetric, area and length terms as well as logarithmic contributions, we derive the corresponding modified Newtonian gravity and derive the expression for planetary orbits. We calculate the shift of the perihelion of Mercury to find bounds to the parameters associated to the modified Newtonian gravity. We compare the parameter associated to the volumetric contribution in the entropy-area relationship with the value derived for galactic rotation curves and the value obtained from the cosmological constant.

gr-qc↗

arXiv2021

Comments On Torsion and MacDowell-Mansouri gravity

Starting with the MacDowell-Mansouri formulation of gravity with a $SO(4,1)$ gauge group, we introduce new parameters into the action to include the non-dynamical Holst term, and the topological Nieh-Yan and Pontryagin classes. Then, we consider the new parameters as fields and analyze the solutions coming from their equations of motion. The new fields introduce torsional contributions to the theory that modify Einstein's equations.

gr-qc↗