arXiv subjects

I. D. D. Carvalho

Publications and source records attributed to I. D. D. Carvalho.

4 recordsLinked to original sources

arXiv2022

Thermodynamics of static and stationary black holes in Einstein-Gauss-Bonnet gravity with dark matter

This paper studies Einstein-Gauss-Bonnet (EGB) black holes surrounded by three phenomenological distributions of dark matter halos. The main result is obtaining the analytical solutions for the metric and all thermodynamic quantities, such as Hawking temperature, entropy, constant-volume heat capacity, and Gibbs free energy for static and stationary black hole solutions. Consequently, we determine a non-null horizon radius at which the black hole halts its evaporation by vanishing the temperature, indicating the emergence of remnants. In the stationary case, we also obtain the ergosphere regions for the found solutions and compare them. Finally, we find local and global phase transitions by studying the behavior of the heat capacity and Gibbs free energy.

gr-qc↗

arXiv2022

Horizon Fractalization in Black Strings Ungravity

In this paper we study the scalar(tensor) and vector unparticle corrections for cosmic and black strings. Initially we have considered an static cosmic string ansatz from which we obtain the solution in terms of first and second kind Bessel functions. We have also obtained the solution for black string in the unparticle scenario. We could identify two regimes, namely, a gravity dominated regime and an ungravity dominated regime. In the gravity dominated regime the black string solution recovers the usual solution for black strings. The Hawking temperature was also studied in both regimes and in the ungravity dominated regime. As in the static and rotating black hole, we found a fractalization of the event horizon. This points to the fact that fractalization is a natural consequence of unparticles. Finally, we study the thermodynamic of the black string in the ungravity scenario by computing the entropy, heat capacity and free energy. For both cases we find that, depending on the region of the parameter $d_U$, we can have phase transitions.

hep-th↗

arXiv2021

Gravitational bending angle with finite distances by Casimir wormholes

In this paper, we investigate the gravitational bending angle due to the Casimir wormholes, which consider the Casimir energy as the source. Furthermore, some of these Casimir wormholes regard Generalized Uncertainty Principle (GUP) corrections of Casimir energy. We use the Ishihara method for the Jacobi metric, which allows us to study the bending angle of light and massive test particles for finite distances. Beyond the uncorrected Casimir source, we consider many GUP corrections, namely: the Kempf, Mangano and Mann (KMM) model, the Detournay, Gabriel and Spindel (DGS) model, and the so-called type II model for the GUP principle. We also find the deflection angle of light and massive particles in the case of the receiver and the source are far away from the lens. In this case, we also compute the optical scalars: convergence and shear for these Casimir wormholes as a gravitational weak lens.

gr-qc↗

arXiv2021

The gravitational bending angle by static and spherically symmetric black holes in bumblebee gravity

This work investigates the influence of the Lorentz symmetry breaking in the bending angle of massive particles and light for bumblebee black hole solutions. The solutions analyzed break the Lorentz symmetry due to a non-zero vacuum expectation value of the bumblebee field. We use the Ishihara method, which allows us to study the bending angle of light for finite distances, and it is applicable to non-asymptotically flat spacetimes when considering the receiver viewpoint. In order to analyze the deflection of massive particles, we systematize the Ishihara method for its application in the Jacobi metric. This systematization allows the study of the deflection angle of massive particles using the Gauss-Bonnet theorem. We consider two backgrounds: the first was found by Bertolami et al. and is asymptotically flat. The second was found recently by Maluf et al. and is not asymptotically flat due to an effective cosmological constant.

gr-qc↗