arXiv subjects

Ricardo Escobedo

Publications and source records attributed to Ricardo Escobedo.

8 recordsLinked to original sources

arXiv2025

Hamiltonian analysis of an Effective action coupled to the Palatini action in 4 dimensions

We carry out the canonical analysis of the coupling of a $4$-dimensional effective action that arises from a dimensional reduction of a $7$-dimensional BF theory to the Palatini action in $4$-dimensions with cosmological constant, focusing on homogeneity and isotropy in all involved fields. We employ Ostrogradsky's methodology because of the presence of second time derivatives. Through the analysis of consistency conditions, we identify three distinct and consistent possibilities. In all these scenarios, we explore the solution of second-class constraints in terms of pairs of canonical variables. Similarly, Hamiltonian analysis is performed only for the $4$-dimensional effective theory. The second-class constraints are solved in terms of canonical coordinates, revealing that this formulation aligns with one of the viable scenarios explored in the coupling to the $4$-dimensional Palatini action, entailing that the $4$-dimensional effective action nullifies gravity.

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arXiv2025

Towards a de Sitter quintom-like cosmology from a reduction of a 7-dimensional $BF$ theory

In this article, we analyze a 7-dimensional $BF$ theory that, upon dimensional reduction, transforms into an effective 4-dimensional action in which a generic metric is involved. A constraint is imposed in such a way that this is the Friedmann-Lemaître-Robertson-Walker metric characterized by a scale factor $a(t)=\mathrm{exp}(H_0 t)$ with a Hubble constant $H_{0}=67.70 \,\rm [km\, s^{-1}\,Mpc^{-1}]$. We also compute the barotropic parameter $ω\equiv p/ρ$ from our solutions. Three different scenarios are explored, in which the model transitions from quintessence to phantom regimes, crossing the theoretical phantom divide line. Consequently, the effective action represents a quintom-like scenario. Moreover, we derive some analytic solutions for the scale factor by treating it as a dynamical variable in the effective action. In this case, different outcomes are obtained, where the model can transit from a cosmological constant to a quintessence regime; however, it cannot cross the theoretical phantom divide line. However, this simplistic model successfully captures distinct phases of cosmic expansion.

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arXiv2023

Post-Newtonian Gravitational Waves with cosmological constant $Λ$ from the Einstein-Hilbert theory

We study the Post-Newtonian approach implemented to the Einstein-Hilbert action adding the cosmological constant $Λ$ at 1PN order. We consider very small values of $Λ$ to derive the Lagrangian of a two body compact system at the center of mass frame at 1PN. Furthermore, the phase function $ϕ(t)$ is obtained from the balance equation and the two polarizations $h_{+}$ and $h_{\times}$ are also calculated. We observe changes due to $Λ$ only at very low frequencies and we notice that it plays the role of "stretch" the spacetime such that both amplitudes become smaller; however, given its nearly negligible value, $Λ$ has no relevance at higher frequencies whatsoever.

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arXiv2022

Fermions coupled to the Palatini action in $n$ dimensions

We study minimal and nonminimal couplings of fermions to the Palatini action in $n$ dimensions ($n\geq 3$) from the Lagrangian and Hamiltonian viewpoints. The Lagrangian action considered is not, in general, equivalent to the Einstein-Dirac action principle. However, by choosing properly the coupling parameters, it is possible to give a first-order action fully equivalent to the Einstein-Dirac theory in a spacetime of dimension four. By using a suitable parametrization of the vielbein and the connection, the Hamiltonian analysis of the general Lagrangian is given, which involves manifestly Lorentz-covariant phase-space variables, a real noncanonical symplectic structure, and only first-class constraints. Additional Hamiltonian formulations are obtained via symplectomorphisms, one of them involving half-densitized fermions. To confront our results with previous approaches, the time gauge is imposed.

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arXiv2021

Straightforward Hamiltonian analysis of $BF$ gravity in $n$ dimensions

We perform, in a manifestly $SO(n-1,1)$ [$SO(n)$] covariant fashion, the Hamiltonian analysis of general relativity in $n$ dimensions written as a constrained $BF$ theory. We solve the constraint on the $B$ field in a way naturally adapted to the foliation of the spacetime that avoids explicitly the introduction of the vielbein. This leads to a form of the action involving a presymplectic structure, which is reduced by doing a suitable parametrization of the connection and then, after integrating out some auxiliary fields, the Hamiltonian form involving only first-class constraints is obtained.

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arXiv2020

Canonical analysis of $BF$ gravity in $n$ dimensions

In this paper we perform in a manifestly $SO(n-1,1)$ [or, alternatively $SO(n)$] covariant fashion, the canonical analysis of general relativity in $n$ dimensions written as a constrained $BF$ theory. Since the Lagrangian action of the theory can be written in two classically equivalent ways, we analyze each case separately. We show that for either action the canonical analysis can be accomplished without introducing second-class constraints during the whole process. Furthermore, in each case the resulting Hamiltonian formulation is the same as the canonical formulation with only first-class constraints recently obtained in M. Montesinos, R. Escobedo, J. Romero, and M. Celada, Phys. Rev. D 101, 024042 (2020) from the $n$-dimensional Palatini action.

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arXiv2020

Canonical analysis of $n$-dimensional Palatini action without second-class constraints

We carry out the canonical analysis of the $n$-dimensional Palatini action with or without a cosmological constant $(n\geq3)$ introducing neither second-class constraints nor resorting to any gauge fixing. This is accomplished by providing an expression for the spatial components of the connection that allows us to isolate the nondynamical variables present among them, which can later be eliminated from the action by using their own equation of motion. As a result, we obtain the description of the phase space of general relativity in terms of manifestly $SO(n-1,1)$ [or $SO(n)$] covariant variables subject to first-class constraints only, with no second-class constraints arising during the process. Afterwards, we perform, at the covariant level, a canonical transformation to a set of variables in terms of which the above constraints take a simpler form. Finally, we impose the time gauge and make contact with the $SO(n-1)$ ADM formalism.

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arXiv2018

$SU(1,1)$ Barbero-like variables derived from Holst action

We work on a spacetime manifold foliated by timelike leaves. In this setting, we explore the solution of the second-class constraints arising during the canonical analysis of the Holst action with a cosmological constant. The solution is given in a manifestly Lorentz-covariant fashion, and the resulting canonical formulation is expressed using several sets of real variables that are related to one another by canonical transformations. By applying a gauge fixing to this formulation, we obtain a description of gravity as an $SU(1,1)$ gauge theory that resembles the Ashtekar-Barbero formulation.

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