arXiv subjects

A. A. Araújo Filho

Publications and source records attributed to A. A. Araújo Filho.

100 records · Page 6Linked to original sources

arXiv2023

Thermodynamics and evaporation of a modified Schwarzschild black hole in a non--commutative gauge theory

In this work, we study the thermodynamic properties on a non--commutative background via gravitational gauge field potentials. This procedure is accomplished after contracting de Sitter (dS) group, $\mathrm{SO}(4,1)$, with the Poincarè group, $\mathrm{ISO}(3,1)$. Particularly, we focus on a static spherically symmetric black hole. In this manner, we calculate the modified Hawking temperature and the other deformed thermal state quantities, namely, entropy, heat capacity, Helmholtz free energy and pressure. Finally, we also investigate the black hole evaporation process in such a context.

hep-th↗

arXiv2022

Particles in Loop Quantum Gravity formalism: a thermodynamical description

In this work, we analyse the thermodynamical behavior of massive and massless particles within Loop Quantum Gravity formalism. We investigate a modified dispersion relation which suffices to derive all our results of interest in an \textit{analytical} manner. Initially, we study the massive case where, in essence, we examine how the mass modifies the thermodynamical properties of the system. On the other hand, to the massless case, the thermodynamical system turns out to rely only on a specific thermal state quantity, the temperature. More so, the analysis of the spectral radiation, the equation of states, the mean energy, the entropy, and the heat capacity are provided as well for both cases. Finally, the thermodynamical properties of our particles under consideration depends on the Riemann zeta function $ξ(s)$.

gr-qc↗

arXiv2022

Fermions on a torus knot

In this work, we investigate the effects of a nontrivial topology (and geometry) of a system considering \textit{interacting} and \textit{noninteracting} particle modes, which are restricted to follow a closed path over the torus surface. In order to present a prominent thermodynamical investigation of this system configuration, we carry out a detailed analysis using statistical mechanics within the grand canonical ensemble approach to deal with \textit{noninteracting} fermions. In an analytical manner, we study the following thermodynamic functions in such context: the Helmholtz free energy, the mean energy, the magnetization and the susceptibility. Further, we take into account the behavior of Fermi energy of the thermodynamic system. Finally, we briefly outline how to proceed in case of \textit{interacting} fermions.

cond-mat.quant-gas↗

arXiv2022

How does geometry affect quantum gases?

In this work, we study the thermodynamic functions of quantum gases confined to spaces of various shapes, namely, a sphere, a cylinder, and an ellipsoid. We start with the simplest situation, namely, a spinless gas treated within the canonical ensemble framework. As a next step, we consider \textit{noninteracting} gases (fermions and bosons) with the usage of the grand canonical ensemble description. For this case, the calculations are performed numerically. We also observe that our results may possibly be applied to \textit{Bose-Einstein condensate} and to \textit{helium dimer}. Moreover, the bosonic sector, independently of the geometry, acquires entropy and internal energy greater than for the fermionic case. Finally, we also devise a model allowing us to perform analytically the calculations in the case of \textit{interacting} quantum gases, and, afterwards, we apply it to a cubical box.

cond-mat.quant-gas↗

arXiv2022

Bouncing universe in a heat bath

We develop a thermal description for photon modes within the context of bouncing universe. Within this study, we start with a Lorentz-breaking dispersion relation which accounts for modified Friedmann equations with a bounce solution. We calculate the spectral radiance, the entropy, the Helmholtz free energy, the heat capacity, and the mean energy. Nevertheless, the latter two ones turn out to contribute only in a trivial manner. Furthermore, one intriguing aspect gives rise to: for some configurations of $η$, $l_{P}$, and $T$, the thermodynamical behavior of the system seems to indicate instability. However, despite of showing this particularity, the solutions of the thermodynamic functions in general turn out to agree with the literature, e.g., the second law of thermodynamics is maintained. More so, all the results are derived \textit{analytically} and three different regimes of temperature of the universe are also considered, i.e., the inflationary era, the electroweak epoch and the cosmic microwave background.

hep-th↗

arXiv2021

Higher-derivative Lorentz-breaking dispersion relations: a thermal description

This paper is devoted to study the thermal aspects of a photon gas within the context of Planck-scale-modified dispersion relations. We study the spectrum of radiation and the correction to the \textit{Stefan$-$Boltzmann} law in different cases when the Lorentz symmetry is no longer preserved. Explicitly, we examine two models within the context of CPT$-$even and CPT$-$odd sectors respectively. To do so, three distinct scenarios of the Universe are considered: the Cosmic Microwave Background (CMB), the electroweak epoch, and the inflationary era. Moreover, the equations of state in these cases turn out to display a dependence on Lorentz-breaking parameters. Finally, we also provide for both theories the analyses of the Helmholtz free energy, the mean energy, the entropy and the heat capacity.

hep-th↗

arXiv2021

Lorentz-violating scenarios in a thermal reservoir

In this work, we analyze the thermodynamic properties of the graviton and the generalized model involving anisotropic Podolsky and Lee$-$Wick terms with Lorentz violation. We build up the so-called partition function from the accessible states of the system seeking the following thermodynamic functions: spectral radiance, mean energy, Helmholtz free energy, entropy and heat capacity. Besides, we verify that, when the temperature rises, the spectral radiance $χ(ν)$ tends to attenuate for fixed values of $ξ$. Notably, when parameter $η_{2}$ increases, the spectral radiance $\barχ(η_{2},ν)$ weakens until reaching a flat characteristic. Finally, for both theories, we perform the calculation of the modified black body radiation and the correction to the $\textit{Stefan-Boltzmann}$ law in the inflationary era of the universe.

hep-th↗

arXiv2021

Thermodynamic properties in higher-derivative electrodynamics

In this work, we study the thermodynamic properties of a photon gas in a heat bath within the context of higher-derivative electrodynamics. Specifically, we analyze Podolsky's theory and its extension involving the Lorentz symmetry violation recently proposed in the literature. First, we use the concept of the number of available states of the system in order to construct the partition function. Next, we calculate the main thermodynamic functions: Helmholtz free energy, mean energy, entropy, and heat capacity. In particular, we verify that there exist significant changes in heat capacity and mean energy due to Lorentz violation. Additionally, the modification of the black body radiation and the correction to the Stefan-Boltzmann law in the context of the primordial inflationary universe are provided for both theories as well.

hep-th↗

arXiv2021

Thermal aspects of interacting quantum gases in Lorentz-violating scenarios

In this work, we study the interaction of quantum gases in Lorentz-violating scenarios considering both boson and fermion sectors. In the latter case, we investigate the consequences of a system governed by scalar, vector, pseudovector and tensor operators. Besides, we examine the implications of $\left( \hat{k}_{a}\right) ^{κ}$ and $\left( \hat{k}_{c}\right) ^{κξ}$ operators for the boson case as well. For doing so, we regard the grand canonical ensemble seeking the so-called partition function, which suffices to provide analytically the calculations of interest, i.e., mean particle number, entropy, mean total energy and pressure. Furthermore, in low temperature regime, such quantities converge until reaching a similar behavior being in contrast with what is shown in high temperature regime, which brings out the differentiation of their effects. In addition, particle number, entropy and energy exhibit an extensive characteristic even in the presence of Lorentz violation. Finally, for peseudovector and tensor operators, we notice a remarkable feature due to the breaking process of spin degeneracy: the system turns out to have greater energy and particle number for the spin-down particles in comparison with spin-up ones.

hep-th↗

arXiv2019

Thermodynamic properties of neutral Dirac particles in the presence of an electromagnetic field

In this paper, we investigate the thermodynamic properties of a set of neutral Dirac particles in the presence of an electromagnetic field in contact with a heat bath for the relativistic and non-relativistic cases. In order to perform the calculations, the high-temperature limit is considered and the Euler-MacLaurin formula is taking into account. Next, we explicitly determine the behavior of the main thermodynamic functions of the canonical ensemble: the Helmholtz free energy, the mean energy, the entropy, and the heat capacity. As a result, we verified that the mean energy and the heat capacity for the relativistic case are two times the values of the non-relativistic case, thus, satisfying the so-called Dulong-Petit law. In addition, we also verified that the Helmholtz free energy and the entropy in both cases increase as a function of the electric field. Finally, we note that there exists no influence on the thermodynamic functions due to the magnetic field.

quant-ph↗