arXiv subjects

S. B. Duarte

Publications and source records attributed to S. B. Duarte.

10 recordsLinked to original sources

arXiv2025

CP-violating non-linear electrodynamics and corrections to blackbody radiation thermal laws

Motivated by ideas from effective field theories, we conduct a twofold investigation in CP-violating non-linear electrodynamics models. On the one hand, features related to field equations and wave propagation in the presence of a magnetic background field are evaluated. Interestingly, we show that the CP-violating term in our framework induces a bi-anisotropic behavior of the vacuum. On the other hand, blackbody radiation thermal laws in this situation are studied. Here, we provide a general formalism for photons at low temperature, namely, with $k_{B}T\ll{m_{e}c^{2}}$. The deviations from standard values of the thermodynamic quantities, such as energy, pressure, entropy, and specific heat, are discussed. In addition, we investigate the modifications in the Planck distribution and the Stefan-Boltzmann law induced by a non-trivial CP-violating parameter.

physics.gen-ph↗

arXiv2024

Nonlinear wave propagation in large extra spatial dimensions and the blackbody thermal laws

Nonlinear wave propagation in large extra spatial dimensions (on and above $d=2$) is investigated in the context of nonlinear electrodynamics theories that depend exclusively on the invariant $\mathcal{F}\left(=-(1/4)F_{μν}F^{μν}\right)$. In this vein, we consider propagating waves under the influence of external uniform electric and magnetic fields. Features related to the blackbody radiation in the presence of a background constant electric field such as the generalization of the spectral energy density distribution and the Stefan-Boltzmann law are obtained. Interestingly enough, anisotropic contributions to the frequency spectrum appear in connection to the nonlinearity of the electromagnetic field. In addition, the long wavelength regime and Wien's displacement law in this situation are studied. The corresponding thermodynamics quantities at thermal equilibrium, such as energy, pressure, entropy, and heat capacity densities are contemplated as well.

hep-th↗

arXiv2024

Quantum gravity phenomenology and the blackbody radiation

We analyze the blackbody radiation problem in the presence of quantum gravity effects encoded in modified dispersion relations. The spectral radiance and the generalized Stefan-Boltzmann law are studied in this context. Furthermore, the regime of low temperatures is also contemplated, where features related to the blackbody thermal laws and the thermodynamic quantities such as energy, pressure, entropy, and specific heat are obtained. Possible implications in compact objects such as neutron stars are also discussed.

gr-qc↗

arXiv2023

Thermodynamics of blackbody radiation in nonlinear electrodynamics

We study the blackbody properties and the thermodynamic equilibrium quantities of a photon gas in the framework of nonlinear electrodynamics. In this vein, we take into account the photon propagation in a uniform external magnetic field in the weak field approximation, where an angular anisotropic energy density distribution appears in the frequency spectrum. The particular case when the photon propagates perpendicular to the background magnetic field is also discussed, which allows us to probe the strong field regime. We then derive a modified blackbody spectral distribution and the Stefan-Boltzmann law in this situation. Considerations about Wien's displacement law and the Rayleigh-Jeans formula are contemplated as well. Deviations from the thermodynamic quantities at thermal equilibrium such as energy, pressure, entropy, and heat capacity densities are obtained from the Helmholtz free energy. As an application, we study three nonlinear electrodynamics, namely, the Euler-Heisenberg, the generalized Born-Infeld, and the logarithmic electrodynamics. Possible implications on stellar systems with strong magnetic fields such as magnetars are discussed.

cond-mat.stat-mech↗

arXiv2023

Neutron Stars in Modified Teleparallel Gravity

We investigate compact objects in modified teleparallel gravity with realistic equations of state. We propose a modification of Teleparallel Equivalent to General Relativity, then an appropriate tetrad is applied to the field equations. A specific set of relations showing an equivalency between our gravitational model and the New General Relativity is found. The conservation equation implies that our Tolman-Oppenheimer-Volkoff equations are presented with an effective gravitational coupling constant. Numerical analysis using realistic equations of state is made, and the behavior of mass, radius, and the relation mass-radius as functions of a free parameter of our model is also investigated.

gr-qc↗

arXiv2022

Equation of state to compact objects with ion crystal lattice

Crystal lattice structure is present in stellar compact objects, such as white dwarf stars and in the crust of neutron stars. These structures can be described by a body-centered cubic crystal, which is formed by ions due to Coulombian interactions in presence of stellar electron plasma. The electron-electron interaction is currently described in the electrodynamics context by a quantum homogeneous plasma. Particularly, we investigate the changes in the medium Equations of State (EoS), improving results presented in the literature. The main purpose of this work is to analyse the distribution of electrons in the stellar medium considering their interaction with ions in the crystal lattice. The electric field produced by the presence of crystal lattice is obtained using linear response theory in the context of finite temperature field theory. The screening and distribution of electrons are corrected by an arbitrary number of neighbor ions, which is a novelty in the literature and significantly impact the EoS. Numerical results are presented for a completely degenerate electron plasma and for different species of ions that make up the lattice. These EoS can be applied to determine the structure of the aforementioned compact stellar objects.

astro-ph.SR↗

arXiv2018

Searching Neutrino-Nucleus Coherent Scattering with Mössbauer Spectroscopy

The Mössbauer technique is proposed as an alternative experimental procedure to be used in the detection of Coherent Elastic $ν$-Nucleus Scattering (CENNS). The $Z_{0}$-boson exchange is considered as a perturbation on the nuclear mean-field potential with a change in the valence neutron quantum states in the $^{57}Fe$ nucleus of the Mössbauer detector sample. This nuclei is a typical isotope used in Mössbauer spectroscopy. Perturbed level of the valence neutron accommodates the transferred energy, modifying the location of the isometric peak of the Mössbauer electromagnetic resonance. We calculate the isometric shift correction due CENNS and show that this quantity is able to be detected with enough precision. Therefore, the difference between the Mössbauer isometric shift in the presence of a reactor-neutrino beam and without the neutrinos flux is pointed out as a figure of merit to manifest CENNS. In this work, we show that the CENNS correction of the Isomeric Shift is of $\approx 10^{-7}$eV, which is greater than the $10^{-10}$eV resolution of the technique.

physics.ins-det↗

arXiv2010

Evaluation of coincidence number of pairs and asymmetry parameter in nonmesonic hypernuclear decay

We develop a theoretical framework for the evaluation of the coincidence number of pairs, $N_{nN}$, and the asymmetry parameter, $a_Λ$, in nonmesonic hypernuclear decay $ΛN\rightarrow nN$. The primary nomesonic weak hyperon-nucleon decay process is described through the independent particle shell model. When the effect of the strong interactions experimented by the two nucleons leaving the residual nucleus is included, we have in addition to the $2p1h$ primary configuration $2p'1h'$, $3p2h$, $4p3h$, $\cdots$, etc secondary ones. We work within the $2p'1h'$ subspace of final states assuming a simple approach for finite nuclei based on the eikonal approximation. An optical potential including the nucleon-nucleus isoscalar and isovector interaction is introduced to take into account the minimum nuclear medium effects and to describe the nucleon-nucleus dispersion process along the outgoing path. We applied the proposed description to the calculation of the observables in $^{5}_ΛHe$ and $^{12}_ΛC$ nonmesonic decays. The calculated results show that our treatment of FSI even considered as restricted to a subspace of states gives a good agreement with experimental data, similar to that ones presented by more elaborated evaluations. This indicates that the developed theoretical scheme seems to be appropriated to include more complex configurations. We also discuss the ground state normalization effects at the moment of including the two-nucleon induced decay ($ΛNN \rightarrow nNN$) contribution.

nucl-th↗

arXiv2008

Gross Theory Model for Neutrino-Nucleus Cross Section

The nuclear gross theory, originally formulated by Takahashi and Yamada for the $β$-decays, is applied for the electronic-neutrino nucleus reactions, employing a more realistic description to the energetics of the Gamow-Teller resonances. The model parameters are gauged from the most recent experimental data, both for $β^-$ decay and electron-capture, separately for even-even, even-odd, odd-odd, odd-even nuclei. The numerical estimates for neutrino-nucleus cross sections agree fairly well with previous evaluations done within the framework of microscopic models. The formalism presented here can be extended to the heavy nuclei mass region, where weak processes are quite relevant, which is of astrophysical interest because of its applications in supernova explosive nucleosynthesis.

nucl-th↗

arXiv2007

Exchange of quantum states between coupled oscillators

Exchange of quantum states between two interacting harmonic oscillator along their evolution time is discussed. It is analyzed the conditions for such exchange starting from a generic initial state and demonstrating that the effect occurs exactly only for the particular states C0|0>+Cn|N>, which includes the interesting qubits components |0>,|1>. It is also determined the relation between the coupling constant and characteristic frequencies of the oscillators to have the complete exchange.

quant-ph↗