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C. C. Barros Jr

Publications and source records attributed to C. C. Barros Jr.

At least 19 recordsLinked to original sources
arXiv2026

Extended Scalar Particle Solutions in Black String Spacetimes with Anisotropic Quintessence

We present novel solutions to the Klein-Gordon equation in a black string spacetime immersed in an anisotropic quintessence fluid and surrounded by a cloud of strings (BCK spacetime). The solutions are shown to depend on the quintessence state parameter $α_{Q}$ and extend to a broader radial domain than previously reported. Explicit analytical results are provided for $α_{Q} = 0, 1/2, 1$, thereby encompassing all relevant physical scenarios. These analytical radial solutions are derived using the confluent and biconfluent Heun equations, as well as Bessel equations in specific cases. Constraints on the Heun parameters that produce spectral restrictions are examined, resulting in the $δ_{N}-$subclass of solutions, which includes the polynomial cases. Quintessence-induced \enquote{dark phases} are identified for several scenarios; in particular, the regime of $α_{Q} = 1$ is emphasized for future comparison with alternative spacetime geometries. These findings contribute to the understanding of scalar particle dynamics and the influence of dark energy on quantum systems in curved spacetime backgrounds.

gr-qc↗
arXiv2026

Curvature Corrections to the Yukawa Potential in Tolman Metrics

This work investigates curvature-induced modifications to the Yukawa potential in static, spherically symmetric spacetimes described by Tolman metrics, focusing on their implications for compact stellar objects, with particular application to solutions IV and VI. Motivated by the interplay of quantum interactions and strong gravitational fields in systems like neutron stars, we derive explicit corrections to the Yukawa potential for these metrics. Contrary to previous findings suggesting that curvature corrections break the radial symmetry of the interacting potential near a highly charged black hole, we demonstrate that Tolman metric corrections preserve this symmetry in the local inertial frame. Numerical estimates for astrophysical objects reveal energy shifts of the order of $10^{-34}$ MeV for solution IV. The Tolman VI solution, while singular at the center, yields comparable corrections for most of the fluid sphere radius. A detailed analysis of the repulsive or attractive nature of these curvature corrections for a local observer is provided for each scenario. These results highlight the role of spacetime geometry in shaping quantum interactions and provide a foundation for future studies of nuclear interactions within the context of relativistic stars.

gr-qc↗
arXiv2026

Kiselev black strings in $f(R,T)$ gravity

In this work, we investigate exact black string solutions in the context of $f(R,T)$ gravity. Adopting the specific form $f(R,T) = R + 2χT$, we consider an anisotropic Kiselev fluid as the matter content and obtain static cylindrical solutions, which are then extended to the rotating case through a suitable coordinate transformation. The influence of the quintessence state parameter $w_q$ and the matter--geometry coupling constant $χ$ on the geometry is analyzed. We examine the weak, null, and strong energy conditions, identifying the regions in the parameter space where they are satisfied. Furthermore, we apply the Hamilton--Jacobi method to study the tunneling of scalar particles across the event horizon and derive the corresponding Hawking temperature. The thermodynamic stability of the solutions is investigated by computing the heat capacity, and the conditions for phase transitions are discussed. The results provide a characterization of black strings in $f(R,T)$ gravity surrounded by quintessence, highlighting the combined effects of anisotropic matter and modified gravity on their physical properties.

gr-qc↗
arXiv2025

Emergence of Dark Phases in Scalar Particles within the Schwarzschild-Kiselev-Letelier Spacetime

This work focuses on the emergence of dark phases (dark energy-induced phases) in the radial wave function of scalar particles. We achieve this by presenting novel solutions to the Klein-Gordon equation in a spherically symmetric spacetime, which encompasses a black hole, a quintessential fluid, and a cloud of strings. We determine the exact solution for the spacetime metric, analyze the admissible ranges for its physical parameters, and discuss the formation of the event horizon. Subsequently, we detail the solution of the Klein-Gordon equation and explore three distinct cases of dark phases, corresponding to the quintessence state parameter $α_{Q}$ taking the values $0$, $1/2$, and $1$. Notably, the case where $α_{Q} = 1$ holds particular significance due to current observational constraints on dark energy.

gr-qc↗
arXiv2025

Charged scalar boson in Melvin universe

This work investigates the dynamics of a charged scalar boson in the Melvin universe by solving the Klein-Gordon equation with minimal coupling in both inertial and non-inertial frames. Non-inertial effects are introduced through a rotating reference frame, resulting in a modified spacetime geometry and the appearance of a critical radius that limits the radial domain of the field. Analytical solutions are obtained under appropriate approximations, and the corresponding energy spectra are derived. The results indicate that both the magnetic field and non-inertial effects modify the energy levels, with additional contributions depending on the coupling between the rotation parameter and the quantum numbers. A numerical analysis is also presented, illustrating the behavior of the solutions for two characteristic magnetic field scales: one that may be considered extreme, of the order of the ones proposed to be produced in heavy-ion collisions and another near the Planck scale.

gr-qc↗
arXiv2025

Spacetime curvature corrections for the Yukawa potential and its application for the Reissner-Nordström Metric

In this paper, we investigate the influence of the spacetime curvature on the Yukawa potential, focusing on boson-boson interactions derived from the {Φ^3} theory. Using the Bunch-Parker propagator expansion within Born's first approximation, we derive a Yukawa-like potential in a curved spacetime. We analyze the impact of the curvature on the propagator in momentum space, revealing modifications to the potential and showing that the corrections are determined by geometric quantities from Einstein's equations, like the Ricci scalar and tensor. We illustrate this using the Reissner-Nordström metric, highlighting the corrections' magnitude for specific parameters. Our results underscore the nuanced interplay between spacetime curvature and quantum interactions, providing insights into nucleon-nucleon systems in curved spacetimes or near strong gravitational fields.

gr-qc↗
arXiv2025

Scalar bosons in Bonnor-Melvin-$Λ$ universe: Exact solution, Landau levels and Coulomb-like potential

In this work, we study spin-0 particles in a spacetime whose structure is determined by a homogeneous magnetic field and a cosmological constant. For this purpose, we take into account a framework based on the Bonnor-Melvin solution with the inclusion of the cosmological constant. We write the Klein-Gordon equation, solve it, and determine the Landau levels. The effects of scalar and vector potentials are considered, and we investigate the influence of the parameters of the theory on the results, which present observable effects. The implications of the physics of a stellar model based on this framework are also discussed.

gr-qc↗
arXiv2024

Klein-Gordon oscillator subject to a Coulomb-type potential in Bonnor-Melvin universe with a cosmological constant

In this work we study spin-0 particles described by the Klein-Gordon oscillator formalism in a spacetime which structure is determined by a homogeneous magnetic field and a cosmological constant. For this purpose we take into account a framework based on the Bonnor-Melvin solution with the inclusion of the cosmological constant. We write and solve the Klein-Gordon equation, and then find the energy spectrum by considering the effect of vector and scalar potentials.

gr-qc↗
arXiv2022

Rapidly rotating compact stars in Rastall's gravity

In this work we study rapidly rotating stars by considering the Rastall theory of gravity. We obtain and solve the equations by numerical methods for two usual parametrization of polytropic stars. Then the mass-radius relations, moments of inertia and other results of interest are obtained and compared with the ones for non-rotating stars.

astro-ph.HE↗
arXiv2019

Fermions in the Rindler spacetime

In this paper we study the Dirac equation in the Rindler spacetime. The solution of the wave equation in an accelerated reference frame is obtained. The differential equation associated to this wave equation is mapped into a Sturm-Liouville problem of a Schrödinger-like equation. We derive a compact expression for the energy spectrum associated with the Dirac equation in an accelerated reference. It is shown that the noninertial effect of the accelerated reference frame mimics an external potential in the Dirac equation and, moreover, allows the formation of bound states.

quant-ph↗
arXiv2019

Klein-Gordon oscillator in a topologically nontrivial space-time

In this study, we analyze solutions of the wave equation for scalar particles in a space-time with nontrivial topology. Solutions for the Klein--Gordon oscillator are found considering two configurations of this space-time. In the first one, it is assumed the $S^{1}\times R^{3}$ space where the metric is written in the usual inertial frame of reference. In the second case, we consider a rotating reference frame adapted to the circle S1. We obtained compact expressions for the energy spectrum and for the particles wave functions in both configurations. Additionally, we show that the energy spectrum of the solution associated to the rotating system has an additional term that breaks the symmetry around $E = 0$.

hep-th↗
arXiv2017

Relativistic quantum motion of spin-0 particles under the influence of non-inertial effects in the cosmic string space-time

We study solutions for the Klein-Gordon equation with vector and scalar potentials of the Coulomb types under the influence of non-inertial effects in the space-time of topological defects. We also investigate a quantum particle described by the Klein-Gordon oscillator in the background space-time generated by a string. An important result obtained is that the non-inertial effects restrict the physical region of the space-time where the particle can be placed. In addition, we show that these potentials can form bound states for the relativistic wave equation equation in this kind of background.

hep-th↗
arXiv2017

Scalar bosons under the influence of noninertial effects in the cosmic string spacetime

In this paper we present two different classes of solutions for the Klein-Gordon equation in the presence of a scalar potential under the influence of noninertial effects in the cosmic string spacetime. We show that noninertial effects restrict the physical region of the spacetime where the particle can be placed, and furthermore that the energy levels are shifted by these effects. In addition, we show that the presence of a Coulomb-like scalar potential allows the formation bound states when the Klein-Gordon equation is considered in this kind of spacetime.

hep-th↗
arXiv2016

Geometrical Aspects of non-gravitational interactions

In this work we look for a geometric description of non-gravitational forces. The basic ideas are proposed studying the interaction between a punctual particle and an electromagnetic external field. For this purpose, we introduce the concept of proper space-time, that allow us to describe this interaction in a way analogous to the one that the general relativity theory does for gravitation. The field equations that define this geometry are similar to the Einstein's equations, where in general, the energy-momentum tensor have information of both, the particle and the external field. In this formalism we consider the particle path as being a geodesic in a curved space-time, and so, the electromagnetic force is understood in a purely geometric way.

gr-qc↗
arXiv2012

The Rarita-Schwinger Particles Under de Influence of Strong Magnetic Fields

In this work, we calculate the solutions of the Rarita-Schwinger equation with the inclusion of the eletromagnetic interaction. Our gauge and coupling prescription choices lead to Dirac-type solutions. One of the consequences of our results are the Landau level occupation of particles, quite different from the usual spin 1/2 particle system occupation numbers.

math-ph↗
arXiv2012

Light clusters and the pasta phase

The effects of including light clusters in nuclear matter at low densities are investigated within four different parametrizations of relativistic models at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase) are described for neutral nuclear matter with fixed proton fractions. We discuss the effect of the density dependence of the symmetry energy, the temperature and the proton fraction on the non-homogeneous matter forming the inner crust of proto-neutron stars. It is shown that the number of nucleons in the clusters, the cluster proton fraction and the sizes of the Wigner Seitz cell and of the cluster are very sensitive to the density dependence of the symmetry energy.

nucl-th↗
arXiv2006

Elements stability: a microcosmos effect?

The electronic structure of heavy elements, when described in a space-time which the metric is affected by the electromagnetic interaction, presents instabilities. These instabilities increase with the atomic number, and above a critical value, become important. The consistency of this theory [1], [2] and a formulation based on the energy-momentum tensor is also investigated. With this procedure, a dynamical cut-off appears in a natural way, and the field equations for the general quantum mechanics are determined.

physics.gen-ph↗