Searcharxiv⌕ Search

arXiv subjects

M. C. Araújo

Publications and source records attributed to M. C. Araújo.

13 recordsLinked to original sources

White Dwarf Stellar Structure from Effective Polymer Geometry in Loop Quantum Gravity

We construct an effective Tolman Oppenheimer Volkoff system for cold carbon white dwarfs using the areal radius form of a polymer metric sector motivated by loop quantum gravity. The two asymptotic mass parameters of the geometry are retained in the stellar prescription through $M_B\rightarrow m(R)$ and $M_W=ηm(R)$, while the polymer amplitude is controlled by $A_λ$. The matter sector is kept fixed and is described by the Chandrasekhar equation of state and by the same carbon model with the Coulomb lattice correction. The resulting equations recover the general relativistic TOV system and the symmetric polymer limit. For the undeformed sequences we obtain $M_{\max}=1.4166\,M_\odot$ for the Chandrasekhar model and $M_{\max}=1.3850\,M_\odot$ when the lattice correction is included. Turning on $A_λ$ shifts the massive part of the equilibrium sequence upward without stiffening the equation of state, reaching $M_{\max}=1.7125\,M_\odot$ and $1.6907\,M_\odot$ at $A_λ=100$ for the two matter models. These configurations remain within the matter domain imposed by the inverse beta decay boundary used in the scan. The asymmetric ratio $η=M_W/M_B$ changes the metric function near the polymer transition region, but its effect on white dwarf observables is small: across the selected configurations, $M_{\max}$ changes by less than $0.1\%$ and the corresponding radius by less than $0.33\%$. The calculation therefore identifies $A_λ$ as the parameter controlling the super Chandrasekhar displacement of the mass radius relation, while $η$ acts mainly as a geometric asymmetry parameter in the low compactness regime probed by white dwarfs.

astro-ph.SR↗

Junction Conditions, Radial Stability, Thermodynamics, Optical Geometry and Appearance of Polymer-Quintessence Thin-Shell Wormholes

Thin-shell wormholes built from effective black hole geometries are sensitive not only to the lapse function but also to the choice of areal radius. We construct a reflection-symmetric thin-shell wormhole from the positive-lapse sector of a polymer black hole surrounded by Kiselev-type quintessence and keep the nonareal angular function throughout the junction, stability, thermodynamic, and optical analyses. The Israel junction conditions give a negative surface energy density for every static throat on the positive branch, while the tangential null and intrinsic strong energy combinations are controlled by the local lapse slope. The radial dynamics is written as an effective-potential problem in which the nonareal sector produces a momentum-flux term and modifies the local stability criterion for surface equations of state with explicit radius dependence. For the sampled calibrated configurations, the linear barotropic and variable phantomlike closures remain locally unstable, whereas the variable Chaplygin gas admits finite linear radial stability windows. The same geometric correction also modifies the local first-law balance and shell entropy bookkeeping, while the optical analysis shows that cross-throat propagation generates additional inner image branches despite the wormhole and black hole geometries sharing the same exterior critical curve. These results identify how polymer corrections and a quintessence environment jointly reorganize the matter content, radial response, thermodynamic bookkeeping, and optical appearance of the resulting thin-shell wormhole.

gr-qc↗

Fermion-fermion scattering in a Rarita-Schwinger model with Yukawa-like interaction

In this work, we investigate the scattering of spin-$3/2$ fermionic particles mediated by a Yukawa-like coupling in the context of the massive Rarita-Schwinger model. The interaction is introduced by replacing $m \to m_ψ + gϕ$ in the free spin-$3/2$ Lagrangian. The analysis is performed at both zero and finite temperatures. In the latter case, thermal effects are incorporated using the Thermofield Dynamics (TFD) formalism. In both regimes, we obtain the differential and total cross sections and examine their behavior in the short-range ($m_ϕ \neq 0$) and long-range ($m_ϕ = 0$) limits, in order to analyze the influence of zero- and finite-temperature effects.

hep-th↗

Rarita-Schwinger model in Very Special Relativity

In this work, we investigate vacuum polarization in the Rarita-Schwinger model within the framework of Very Special Relativity. We examine both massive and massless spin-3/2 fields coupled to the Maxwell field. The Mandelstam-Leibbrandt prescription is applied in order to evaluate the one-loop integrals, and we work within the SIM(2) limit.

hep-th↗

Polymer Black Hole Surrounded by Quintessence

In this paper, we study the polymer black hole solution surrounded by a quintessence field. The influence of quintessence on the polymer black hole is investigated through its thermodynamic properties, such as the Hawking temperature, entropy, and specific heat, which allow us to address the question of thermodynamic stability. We then calculate bounds on the electromagnetic greybody factors and photon emission rates of the black hole, highlighting the interplay between quintessence and quantum gravity effects in determining these phenomena. We also examine the effects of quintessence and quantum gravity on the geodesics and shadows of massless particles around the black hole. Our results are further compared with observational data of the Sagittarius A black hole from the Event Horizon Telescope (EHT) collaboration.

gr-qc↗

Lorentz-violating QED inspired superconductivity

We studied a Lorentz-violating inspired Ginzburg-Landau model for superconductivity where we considered a CPT-odd contribution given by $(k_{AF})^μ$, also known as the Carroll-Field-Jackiw term. In the static limit of the equations, we could find a pair of modified Ginzburg-Landau equations. Furthermore, these equations were reduced to the London equation for the magnetic field when assumed that the characteristic length of the order parameter is much smaller than the characteristic length of the magnetic field, i.e. the London penetration length. Our numerical solutions showed a simple Meissner state when this new term is small compared to $λ_L$ and a phase transition into phases with strong in-plane currents and anomalous vortices for large contributions. This model becomes useful in exemplifying the changes in the phenomenology of superconductors when the setup of the system shows an important breakdown of Lorentz invariance. Based on these results, we discuss how such models might be the hallmark of unusual superconducting states where there is a direction where the system shows stratification, as in anapole superconductors UTe$_2$.

cond-mat.supr-con↗

Bhabha-like scattering in the Rarita-Schwinger model at finite temperature

In this paper, we study a Bhabha-like scattering in a massive Rarita-Schwinger model at finite temperature. The analysis is conducted at the tree level and addresses temperature effects through the thermofield dynamics formalism. We consider the usual fermion-antifermion into fermion-antifermion scattering and compute the cross-section in order to investigate the influence of the finite temperature effects.

hep-th↗

Electronic states in a bilayer graphene quantum ripple

In this paper, we investigate the influence of the geometry in the electronic states of a quantum ripple surface. We have considered an electron governed by the spinless stationary Schrödinger equation constrained to move on the ripple surface due to a confining potential from which the Da Costa potential emerges. We investigate the role played by the geometry and orbital angular momentum on the electronic states of the system.

cond-mat.mes-hall↗

Anisotropic Ginzburg-Landau model for superconductivity with five-dimensional operators

This paper presents the effects of non-minimal Lorentz-violation operators in superconductivity. By constructing a Lorentz-Violating Ginzburg-Landau theory of superconductivity with a five-dimensional operator, we discuss the influence of higher dimensional Lorentz-Violating operators in the London's depth penetration, in the coherence length and critical magnetic field.

hep-th↗

Meson scattering in a non-minimally Lorentz-violating scalar QED at finite temperature

In this paper we study meson scattering in a non-minimally Lorentz-violating scalar QED at finite temperature. The meson scatterings were investigated in tree level and the finite temperature effects were addressed by using the thermofield dynamics formalism. We have considered three types of scattering, namely, meson-antimeson of $a$-type into meson-antimeson of $b$-type, meson-antimeson of $a$-type into meson-antimeson of $a$-type and meson-meson of $a$-type into meson-meson of $a$-type. For each scattering we have computed the cross section in order to investigate the influence of the finite temperature effects.

hep-th↗

Lorentz-violating extension of scalar QED at finite temperature

In this work, we calculate the one-loop self-energy corrections to the gauge field in scalar electrodynamics modified by Lorentz-violating terms within the framework of the standard model extension (SME). We focus on both $CPT$-even and $CPT$-odd contributions. The kinetic part of the scalar sector contains a $CPT$-even symmetric Lorentz-breaking tensor, and the interaction terms include a vector contracted with the usual covariant derivative in a gauge-invariant manner. We computed the one-loop radiative corrections using dimensional regularization for both the $CPT$-even and $CPT$-odd cases. Additionally, we employed the Matsubara formalism to account for finite temperature effects.

hep-th↗

Casimir effect in a Lorentz-violating tensor extension of a scalar field theory

This paper investigates the Casimir Energy modifications due to the Lorentz-violating CPT-even contribution in an extension of the scalar QED. We have considered the complex scalar field satisfying Dirichlet boundary conditions between two parallel plates separated by a small distance. An appropriate tensor parametrization allowed us to study the Casimir effect in three setups: isotropic, anisotropic parity-odd, and anisotropic parity-even. We have shown that the Lorentz-violating contributions promote increased Casimir energy for both the isotropic and anisotropic parity-odd configurations. However, in the parity-even case, the Lorentz-violating terms can promote either an increase or a decrease in the Casimir energy. We have shown that both the increased and decreased amounts in the Casimir energy depend on the momentum projection over the Lorentz-violating vectors.

hep-th↗

Meson scattering in a Lorentz-violating scalar QED at finite temperature

This paper investigates how the nonzero temperature affects the differential cross-section for mesons scattering in a Lorentz-violating extension of the scalar electrodynamics. We initially discuss some features of the model and extract the zero temperature Feynman rules. Temperature effects are introduced using the Thermo Field Dynamics (TFD) formalism. It is shown that the corrections induced on the meson scattering are very large in the high-temperature regime. Furthermore, our results also suggest that temperature effects may contribute to new constraints on the Lorentz-violating parameters.

hep-ph↗