Heidari, N., Hassanabadi, H., Araujo Filho, A. A., Kriz, J., Zare, S., & Porfirio, P. J. (2024). Gravitational signatures of a non-commutative stable black hole. Phys. Dark Universe, 43, 101382–13pp.
Abstract: This work investigates several key aspects of a non-commutative theory with mass deformation. We calculate thermodynamic properties of the system and compare our results with recent literature. We examine the quasinormal modes of massless scalar perturbations using two approaches: the WKB approximation and the Poschl-Teller fitting method. Our results indicate that stronger non-commutative parameters lead to slower damping oscillations of gravitational waves and higher partial absorption cross sections. Furthermore, we study the geodesics of massless and massive particles, highlighting that the non-commutative parameter (R) significantly impacts the paths of light and event horizons. Also, we calculate the shadows, which show that larger values of (R) correspond to larger shadow radii, and provide some constraints on (R) applying the observation of Sgr A* from the Event Horizon Telescope. Finally, we explore the deflection angle in this context.
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Araujo Filho, A. A., Jusufi, K., Cuadros-Melgar, B., & Leon, G. (2024). Dark matter signatures of black holes with Yukawa potential. Phys. Dark Universe, 44, 101500–20pp.
Abstract: This study uses a nonsingular Yukawa-modified potential to obtain a static and spherically symmetric black hole solution with a cosmological constant. Such Yukawa-like corrections are encoded in two parameters, alpha and lambda, that modify Newton's law of gravity in large distances, and a deformation parameter l(0), which plays an essential role in short distances. The most significant effect is encoded in alpha, which modifies the total black hole mass with an extra mass proportional to alpha M, mimicking the dark matter effects at large distances from the black hole. On the other hand, the effect due to lambda is small for astrophysical values. We scrutinize the quasinormal frequencies and shadows associated with a spherically symmetric black hole and the thermodynamical behavior influenced by the Yukawa potential. In particular, the thermodynamics of this black hole displays a rich behavior, including possible phase transitions. We use the WKB method to probe the quasinormal modes of massless scalar, electromagnetic, and gravitational field perturbations. In order to check the influence of the parameters on the shadow radius, we consider astrophysical data to determine their values, incorporating information on an optically thin radiating and infalling gas surrounding a black hole to model the black hole shadow image. In particular, we consider Sgr A* black hole as an example and we find that its shadow radius changes by order of 10(-9), meaning that the shadow radius of a black hole with Yukawa potential practically gives rise to the same result encountered in the Schwarzschild black hole. Also, in the eikonal regime, using astrophysical data for Yukawa parameters, we show that the value of the real part of the QNMs frequencies changes by 10(-18). Such Yukawa-like corrections are, therefore, difficult to measure by observations of gravitational waves using the current technology.
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Araujo Filho, A. A., Jusufi, K., Cuadros-Melgar, B., Leon, G., Jawad, A., & Pellicer, C. E. (2024). Charged black holes with Yukawa potential. Phys. Dark Universe, 46, 101711–16pp.
Abstract: This study derives a novel family of charged black hole solutions featuring short- and long-range modifications. These are achieved through a Yukawa-like gravitational potential modification and a nonsingular electric potential incorporation. The short-range corrections encode quantum gravity effects, while the long-range adjustments simulate gravitational effects akin to those attributed to dark matter. Our investigation reveals that the total mass of the black hole undergoes corrections owing to the apparent presence of dark matter mass and the self-adjusted electric charge mass. Two distinct solutions are discussed: a regular black hole solution characterizing small black holes, where quantum effects play a crucial role, and a second solution portraying large black holes at considerable distances, where the significance of Yukawa corrections comes into play. Notably, these long-range corrections contribute to an increase in the total mass and hold particular interest as they can emulate the role of dark matter. Finally, we explore the phenomenological aspects of the black hole. Specifically, we examine the influence of electric charge and Yukawa parameters on thermodynamic quantities, the quasinormal modes for the charged scalar perturbations as well as for the vector perturbations, analysis of the geodesics of light/massive particles, and the accretion of matter onto the charged black hole solution.
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Olmo, G. J., Rubiera-Garcia, D., & Sanchez-Puente, A. (2016). Impact of curvature divergences on physical observers in a wormhole space-time with horizons. Class. Quantum Gravity, 33(11), 115007–12pp.
Abstract: The impact of curvature divergences on physical observers in a black hole space-time, which, nonetheless, is geodesically complete is investigated. This space-time is an exact solution of certain extensions of general relativity coupled to Maxwell's electrodynamics and, roughly speaking, consists of two Reissner-Nordstrom (or Schwarzschild or Minkowski) geometries connected by a spherical wormhole near the center. We find that, despite the existence of infinite tidal forces, causal contact is never lost among the elements making up the observer. This suggests that curvature divergences may not be as pathological as traditionally thought.
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Araujo Filho, A. A., Zare, S., Porffrio, P. J., Kriz, J., & Hassanabadi, H. (2023). Thermodynamics and evaporation of a modified Schwarzschild black hole in a non-commutative gauge theory. Phys. Lett. B, 838, 137744–9pp.
Abstract: 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, SO(4, 1), with the Poincare group, 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.
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