arXiv subjects

S. Pérez-Payán

Publications and source records attributed to S. Pérez-Payán.

11 recordsLinked to original sources

arXiv2023

Noncommutative effective LQC: A (pre-)inflationary dynamics investigation

We conduct a (pre-)inflationary dynamics study within the framework of a simple noncommutative extension of effective loop quantum cosmology -- put forward recently by the authors -- which preserves its key features (in particular, the quantum bounce is maintained). A thorough investigation shows that the (pre-)inflationary scenario associated to the chaotic quadratic potential is in the overall the same as the one featured in standard loop quantum cosmology (which reinforces the conclusion reached by the authors in a preliminary analysis). Hence, this (pre-)inflationary scenario does not easily distinguish between standard loop quantum cosmology and the aforementioned noncommutative scheme. It is argued that a particular tuning of the noncommutativity parameter could accommodate for subtle effects at the level of primordial perturbations (the hybrid quantization framework being a tentative route of analysis).

gr-qc↗

arXiv2023

Quintom fields from chiral anisotropic cosmology

In this paper we present an analysis of a chiral anisotropic cosmological scenario from the perspective of quintom fields. In this setup quintessence and phantom fields interact in a non-standard (chiral) way within an anisotropic Bianchi type I background. We present our examination from two fronts: classical and quantum approaches. In the classical program we find analytical solutions given by a particular choice of the emerged relevant parameters. Remarkably, we present an explanation of the ''big-bang'' singularity by means of a ''big-bounce''. Moreover, isotropization is in fact reached as the time evolves. On the quantum counterpart the Wheeler-DeWitt equation is analytically solved for various instances given by the same parameter space from the classical study, and we also include the factor ordering $\rm Q$. Having solutions in this scheme we compute the probability density, which is in effect damped as the volume function and the scalar fields evolve; and it also tends towards a flat FLRW framework when the factor ordering constant $\rm Q \ll 0$. This result might indicate that for a fixed set of parameters, the anisotropies quantum-mechanically vanish for very small values of the parameter $\rm Q$. Finally, classical and quantum solutions reduce to their flat FLRW counterparts when the anisotropies vanish.

gr-qc↗

arXiv2022

Quintom fields from chiral K-essence cosmology

In this paper, we present an analysis of a chiral cosmological scenario from the perspective of K-essence formalism. In this setup, several scalar fields interact within the kinetic and potential sectors. However, we only consider a flat Friedmann--Robertson--Lama\^ıtre--Walker universe coupled minimally to two quintom fields: one quintessence and one phantom. We examine a classical cosmological framework, where analytical solutions are obtained. Indeed, we present an explanation of the ``big-bang'' singularity by means of a ``big-bounce''. Moreover, having a barotropic fluid description and for a particular set of parameters, the phantom line is in fact crossed. Additionally, for the quantum counterpart, the Wheeler--DeWitt equation is analytically solved for various instances, where the factor-ordering problem has been taken into account (measured by the factor Q). Hence, this approach allows us to compute the probability density of the previous two classical subcases. It turns out that its behavior is in effect damped as the scale factor and the scalar fields evolve. It also tends towards the phantom sector when the factor ordering constant $\rm Q\ll 0$.

gr-qc↗

arXiv2021

Anisotropic chiral cosmology: exact solutions

In this work, we investigate the anisotropic Bianchi type I cosmological model in the chiral setup, in a twofold manner. Firstly, we consider a quintessence plus a k-essence like model, where two scalar fields but only one potential term is considered. Secondly, we look at a model where in addition to the two scalar fields the two potential terms are taken into account as well as the standard kinetic energy and the mixed term. Regarding this second model, it is shown that two possible cases can be studied: a quintom like case and a quintessence like case. In each of the models, we were able to find both classical and quantum analytical solutions.

gr-qc↗

arXiv2021

Classical and quantum exact solutions for a FRW in chiral like cosmology

In this work, first, we study a flat Friedmann-Robertson-Walker Universe with two scalar fields but only one potential term, which can be thought as a simple quintessence plus a K-essence model. Employing the Hamiltonian formalism we are able to obtain the classical and quantum solutions. The second model studied, is also a flat Friedmann-Robertson-Walker Universe with two scalar fields, with the difference that the two potentials are considered as well as the standard kinetic energy and the mixed term (chiral field approach). Regarding this second model, it is shown that setting to zero the coefficient accompanying the mixed momenta term, two possible cases can be studied: a quintom like case ($m^{12}_{+}$) and a quintessence like case ($m^{12}_{-}$). For both scenarios classical and quantum solutions are presented.

gr-qc↗

arXiv2021

Noncommutative Effective LQC: inclusion of potential term

We construct and study a simple noncommutative scheme (theta-deformation) for the effective Loop Quantum Cosmology of the flat Friedmann-Lemaître-Robertson-Walker model in the presence of a homogeneous scalar field $ϕ$ with a potential $\mathcal{V}(ϕ)=\frac{1}{2}m^2ϕ^2$. We first conduct a simple analysis from the corresponding Hamilton equations of motion considering a generic term $\mathcal V(ϕ)$. It is observed that the characteristic Big Bounce of Loop Quantum Cosmology is preserved under such noncommutative extension. When specializing to the quadratic case, numerical solutions to the corresponding Hamilton equations exhibiting an early inflationary epoch with a sufficiently large number of e-foldings are found. It is concluded that, in this noncommutative setup, solutions exist which are in the overall compatible with the early universe predicted by standard (effective) Loop Quantum Cosmology (i.e. a bouncing and inflationary early universe). The issue of the genericness of a sufficiently long inflationary period on the space of solutions in this noncommutative construct remains to be addressed.

gr-qc↗

arXiv2020

Cosmological volume acceleration in dust epoch: using scaling solutions and variable cosmological term $Λ(t)$ within an anisotropic cosmological model

Under the premise that the current observations of the cosmic microwave background radiation set a very stringent limit to the anisotropy of the universe, we consider an anistropic model in the presence of a barotropic perfect fluid and a homogeneous scalar field, which transits to a flat FRW cosmology for late times in a dust epoch, presenting an accelerated volume expansion. Furtheremore, the scalar field is identified with a varying cosmological term via $V(ϕ(t))=2Λ(t)$. Exact solutions to the EKG system are obtained by proposing an anisotropic extension of the scaling solutions scenario: $\rmρ\sim η^{-n},\ ρ_ϕ\sim η^{-m}$, with $\rmη^3=a_1a_2a_3$ the volume function of the anistropic model ($\rm a_1,\, a_2,\, a_3$ being the scale factors).

gr-qc↗

arXiv2019

Noncommutative Friedmann Equations in Effective LQC

In this work we construct a noncommutative version of the Friedmann equations in the framework of effective loop quantum cosmology, extending and applying the ideas presented in a previous proposal by some of the authors. The model under consideration is a flat FRW spacetime with a free scalar field. First, noncommutativity in the momentum sector is introduced. We establish the noncommutative equations of motion and obtain the corresponding exact solutions. Such solutions indicate that the bounce is preserved, in particular, the energy density is the same as in standard LQC. We also construct a noncommutative version of the modified Friedmann equations and argue that, as a consequence of noncommutativity, an effective potential arises. This, in turn, leads us to investigate the possibility of an inflationary era. Finally, we obtain the Friedmann and the Raychaudhuri equations when implementing noncommutativity in the configuration sector. In this case, no effective potential is induced.

gr-qc↗

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↗

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↗