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M. Sabido

Publications and source records attributed to M. Sabido.

At least 37 records · Page 2Linked to original sources
arXiv2021

Comments on the symmetry breaking condition in MacDowell-Mansouri action

In this work we study the symmetry breaking conditions, given by a (anti)de Sitter-valued vector field, of a full (anti)de Sitter-invariant MacDowell-Mansouri inspired action. We show that under these conditions the action breaks down to General Relativity with a cosmological constant, the four dimensional topological invariants, as well as the Holst term. We obtain the equations of motion of this action, and analyze the symmetry breaking conditions.

hep-th↗
arXiv2020

BTZ entropy from topological M-theory

By determining the relation between topological M-theory and the Chern-Simons actions for a gauge field constructed from the Lie algebra of either SL(2,R)x SL(2,R) or SL(2,C)x SL(2,C), depending on the sign of the space-time curvature, we show that the standard and exotic actions of 3-dimensional gravity can be recovered from topological M-theory. With this result, we provide a concrete realisation of a conjecture by Dijkgraaf et al. stating that the partition function of topological M-theory is equivalent to the partition function of a black hole in a related theory. We do this for the standard and exotic BTZ black holes in 3-dimensional gravity.

hep-th↗
arXiv2019

On Emergent Gravity, Ungravity and $Λ$

In this paper we study the "ungravity" modifications to the Friedmann equations. By using the first law of thermodynamics and the modified entropy area relationship derived from the "ungravity" contributions to the Schwarzschild black hole, we obtain modifications to the Friedmann equation that in the late time regime gives an effective cosmological constant. Therefore, this simple model can provide an "ungravity" origin to the cosmological constant $Λ$.

gr-qc↗
arXiv2018

An Effective Cosmological Constant From an Entropic Formulation of Gravity

We use the ideas of entropic gravity to derive the FRW cosmological model and show that for late time evolution we have an effective cosmological constant. By using the first law of thermodynamics and the modified entropy area relationship derived from the supersymmetric Wheeler-DeWitt equation of the Schwarzschild black hole, we obtain modifications to the Friedmann equations that in the late time regime gives an effective positive cosmological constant. Therefore, this simple model can account for the dark energy component of the universe by providing an entropic origin to the cosmological constant $Λ$.

gr-qc↗
arXiv2018

On Emergent Gravity, Black Hole Entropy and Galactic Rotation Curves

In this work we derive a generalized Newtonian gravitational force and show that it can account for the anomalous galactic rotation curves. We derive the entropy-area relationship applying the Feynman-Hibbs procedure to the supersymmetric Wheeler-DeWitt equation of the Schwarzschild black hole. We obtain the modifications to the Newtonian gravitational force from the entropic formulation of gravity.

gr-qc↗
arXiv2018

Phase space deformations in phantom cosmology

We discuss the physical consequences of making general phase space deformations on the minisuperspace of phantom cosmology. Based on the principle of physically equivalent descriptions in the deformed theory, we investigate for what values of the deformation parameters the arising descriptions are physically equivalent. We also construct and solve the quantum model and derive the semiclassical dynamics.

gr-qc↗
arXiv2017

On the Entropy of Deformed Phase Space Black Hole and the Cosmological Constant

In this paper we study the effects of noncommutative phase space deformations on the Schwarzschild black hole. This idea has been previously studied in {Friedmann-Robertson-Walker (FRW)} cosmology, where this "noncommutativity" provides a simple mechanism that can explain the origin of the cosmological constant. In this paper we obtain the same relationship between the cosmological constant and the deformation parameter that appears in deformed phase space cosmology, but in the context of the deformed phase space black holes. This was achieved by comparing the entropy of the deformed Schwarzschild black hole with the entropy of the Schwarzschild-de Sitter black hole.

gr-qc↗
arXiv2016

Self-Dual Gravity and the Immirzi parameter

Working in the first order formalism of gravity, we propose an action that combines the self and anti-self-dual parts of the curvature and comprises all the diffeomorphism invariant Lagrangians that one can consider in this formalism. The action that we propose is motivated by (A)dS gauge theories of gravity. We use this action to derive the (2+1)-dimensional version of the Immirzi parameter. Our derivation relates explicitly the Immirzi parameter to the existence of two classically equivalent actions for the description of gravity in (2+1) dimensions, namely the standard and exotic actions introduced by Witten in the description of (2+1) gravity as a gauge theory. This relation had been conjectured previously in the literature, but not derived.

gr-qc↗
arXiv2015

Anistropic Invariant FRW Cosmology

In this paper we study the effects of including anisotropic scaling invariance in the minisuperspace Lagrangian for a universe modelled by the Friedman-Robertson-Walker metric, a massless scalar field and cosmological constant. We find that canonical quantization of this system leads to a Schroedinger type equation, thus avoiding the frozen time problem of the usual Wheeler-DeWitt equation. Furthermore, we find numerical solutions for the classical equations of motion, and we also find evidence that under some conditions the big bang singularity is avoided in this model.

gr-qc↗
arXiv2015

Deformed Phase Space Kaluza-Klein cosmology and late time acceleration

The effects of phase space deformations on Kalutza-Klein cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables. In the deformed model, we find an accelerating scale factor and therefore infer the existence of an effective cosmological constant from the phase space deformation parameter $β$.

gr-qc↗
arXiv2013

Slow-Roll Inflation in Non-geometric Flux Compactification

By implementing a genetic algorithm we search for stable vacua in Type IIB non-geometric flux compactification on an isotropic torus with orientifold 3-planes. We find that the number of stable dS and AdS vacua are of the same order. Moreover we find that in all dS vacua the multi-field slow-roll inflationary conditions are fulfilled. Specifically we observe that inflation is driven by the axio-dilaton and the Kähler moduli. We also comment on the existence of one stable dS vacuum in the presence of exotic orientifolds.

hep-th↗
arXiv2013

On Deformed Phase Space and $Λ$

In this letter we study the effects of a noncommutative in the phase space of an empty (4+1) Kaluza-Klein universe with cosmological constant. We analyze the effects of the noncommutative deformations on the cosmological constant. Finally we comment on the possibility that the origin of the cosmological constant in this model, is related to the noncommutativity between the 4 dimensional scale factor and the compact extra dimension.

hep-th↗
arXiv2013

Toward Supergravity Spectral Action

A spectral action of Euclidean supergravity is proposed. We calculate up to $a_4$, the Seeley-Dewitt coefficients in the expansion of the spectral action associated to the supergravity Dirac operator. This is possible because in simple supergravity, as in pure gravity, a well defined and mathematically consistent Dirac operator can be constructed.

hep-th↗
arXiv2012

Conformal Anisotropic Quantum Cosmology

In this paper we apply the ideas put forward by Hořava, and introduce anisotropic transformations to cosmology. We start with the Kantowski-Sachs cosmological model and impose anisotropic transformation invariance on the minisuperspace variables. We study the symmetries of the anisotropic model and by canonical quantization find a Schrödinger type equation for $z\ne 1$. Finally, we conclude that introducing anistropic invariance can be considered a solution to the problem of time in quantum cosmology and gives some insight on the structure of a well behaved quantum theory of gravity.

hep-th↗
arXiv2012

Effects of deformed phase space on scalar field cosmology

The effects of phase space deformations in standard scalar field cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables to have a deformed Poisson algebra among the coordinates and the canonical momenta. It is found that in the deformed minisuperspace model the volume of the universe is non singular. Finally, the late time evolution gives rise to an accelerating scale factor, this acceleration is a consequence of the noncommutative deformation.

hep-th↗
arXiv2012

Black Hole Thermodynamics from a Noncommutative Area Operator

One key element to calculate thermodynamical properties for a black hole is the partition function. In this paper we have incorporated the idea of a two dimensional area in a noncommutative space and were able to calculate the partition function with such a spectra. Employing the canonical quantum statistics formalism we compute the temperature, entropy and time of evaporation for a Schwarzschild black hole.

hep-th↗
arXiv2009

Classical and quantum Cosmology of the Sáez-Ballester theory

We study the generalization of the Sáez-Ballester theory applied to a flat FRW cosmological model. Classical exact solutions up to quadratures are easily obtained using the Hamilton-Jacobi approach. Contrary to claims in the specialized literature, it is shown that the Sáez-Ballester theory cannot provide a realistic solution to the dark matter problem of Cosmology. Furthermore the quantization procedure of the theory can be simplified by reinterpreting the theory in the Einstein frame, where the scalar field can be interpreted as part of the matter content of the theory, in this approach, exact solutions are also found for the Wheeler-DeWitt equation in the quantum regime.

gr-qc↗