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Guerrero, M., Olmo, G. J., Rubiera-Garcia, D., & Saez-Chillon Gomez, D. (2021). Shadows and optical appearance of black bounces illuminated by a thin accretion disk. J. Cosmol. Astropart. Phys., 08(8), 036–19pp.
Abstract: We study the light rings and shadows of an uniparametric family of spherically symmetric geometries interpolating between the Schwarzschild solution, a regular black hole, and a traversable wormhole, and dubbed as black bounces, all of them sharing the same critical impact parameter. We consider the ray-tracing method in order to study the impact parameter regions corresponding to the direct, lensed, and photon ring emissions, finding a broadening of all these regions for black bounce solutions as compared to the Schwarzschild one. Using this, we determine the optical appearance of black bounces when illuminated by three standard toy models of optically and geometrically thin accretion disks viewed in face-on orientation.
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Olmo, G. J., & Rubiera-Garcia, D. (2015). The quantum, the geon and the crystal. Int. J. Mod. Phys. D, 24(9), 1542013–15pp.
Abstract: Effective geometries arising from a hypothetical discrete structure of spacetime can play an important role in the understanding of the gravitational physics beyond General Relativity (GR). To discuss this question, we make use of lessons from crystalline systems within solid state physics, where the presence of defects in the discrete microstructure of the crystal determine the kind of effective geometry needed to properly describe the system in the macroscopic continuum limit. In this work, we study metric-affine theories with nonmetricity and torsion, which are the gravitational analog of crystalline structures with point defects and dislocations. We consider a crystal-motivated gravitational action and show the presence of topologically nontrivial structures (wormholes) supported by an electromagnetic field. Their existence has important implications for the quantum foam picture and the effective gravitational geometries. We discuss how the dialogue between solid state physics systems and modified gravitational theories can provide useful insights on both sides.
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Santos, A. C. L., Muniz, C. R., & Maluf, R. V. (2023). Yang-Mills Casimir wormholes in D=2+1. J. Cosmol. Astropart. Phys., 09(9), 022–24pp.
Abstract: This work presents new three-dimensional traversable wormhole solutions sourced by the Casimir density and pressures related to the quantum vacuum fluctuations in Yang-Mills (Y-M) theory. We begin by analyzing the noninteracting Y-M Casimir wormholes, initially considering an arbitrary state parameter omega and determine a simple constant wormhole shape function. Next, we introduce a new methodology for deforming the state parameter to find well-behaved redshift functions. The wormhole can be interpreted as a legitimate Casimir wormhole with an expected average state parameter of omega = 2. Then, we investigate the wormhole curvature properties, energy conditions, and stability. Furthermore, we discover a novel family of traversable wormhole solutions sourced by the quantum vacuum fluctuations of interacting Yang-Mills fields with a more complex shape function. Deforming the effective state parameter similarly, we obtain well-behaved redshift functions and traversable wormhole solutions. Finally, we examine the energy conditions and stability of solutions in the interacting scenario and compare to the noninteracting case.
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Galli, P., Ortin, T., Perz, J., & Shahbazi, C. S. (2012). From supersymmetric to non-supersymmetric black holes. Fortschritte Phys.-Prog. Phys., 60(9-10), 1026–1029.
Abstract: Methods similar to those used for obtaining supersymmetric black hole solutions can be employed to find also non-supersymmetric solutions. We briefly review some of them, with the emphasis on the non-extremal deformation ansatz of [1].
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