P. A. González

Exact charged black-hole solutions in D-dimensional f (T) gravity: torsion vs curvature analysis

A bstractWe extract exact charged black-hole solutions with flat transverse sections in the framework of D-dimensional Maxwell-f (T) gravity, and we analyze the singularities and horizons based on both torsion and curvature invariants. Interestingly enough, we find that in some particular solution subclasses there appear more singularities in the curvature scalars than in the torsion ones. This difference disappears in the uncharged case, or in the case where f (T) gravity becomes the usual linear-in-T teleparallel gravity, that is General Relativity. Curvature and torsion invariants behave very differently when matter fields are present, and thus f (R) gravity and f (T) gravity exhibit different features and cannot be directly re-casted each other.

Circularly symmetric solutions in three-dimensional teleparallel, f (T ) and Maxwell-f (T ) gravity

A bstractWe present teleparallel 3D gravity and we extract circularly symmetric solutions, showing that they coincide with the BTZ and Deser-de-Sitter solutions of standard 3D gravity. However, extending into f (T ) 3D gravity, that is considering arbitrary functions of the torsion scalar in the action, we obtain BTZ-like and Deser-de-Sitter-like solutions, corresponding to an effective cosmological constant, without any requirement of the sign of the initial cosmological constant. Finally, extending our analysis incorporating the electromagnetic sector, we show that Maxwell-f (T ) gravity accepts deformed charged BTZ-like solutions. Interestingly enough, the deformation in this case brings qualitatively novel terms, contrary to the pure gravitational solutions where the deformation is expressed only through changes in the coefficients. We investigate the singularities and the horizons of the new solutions, and amongst others we show that the cosmic censorship can be violated. Such novel behaviors reveal the new features that the f (T ) structure brings in 3D gravity.

Four-Dimensional Asymptotically AdS Black Holes with Scalar Hair

A bstractWe present a new family of asymptotically AdS four-dimensional black hole solutions with scalar hair of a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential. For a certain profile of the scalar field we solve the Einstein equations and we determine the scalar potential. Thermodynamically we show that there is a critical temperature below which there is a phase transition of a black hole with hyperbolic horizon to the new hairy black hole configuration.

Quasinormal modes and Stability Analysis for 4-dimensional Lifshitz Black Hole

We study the Lifshitz black hole in four dimensions with dynamical exponent z = 2 and we calculate analytically the quasinormal modes of scalar perturbations. These quasinormal modes allow to study the stability of the Lifshitz black hole and we have obtained that Lifshitz black hole is stable.

Quasinormal modes, stability analysis and absorption cross section for 4-dimensional topological Lifshitz black hole

We study scalar perturbations in the background of a topological Lifshitz black hole in four dimensions. We compute analytically the quasinormal modes and from these modes we show that topological Lifshitz black hole is stable. On the other hand, we compute the reflection and transmission coefficients and the absorption cross section and we show that there is a range of modes with high angular momentum which contributes to the absorption cross section in the low frequency limit. Furthermore, in this limit, we show that the absorption cross section decreases if the scalar field mass increases, for a real scalar field mass.

Dirac quasinormal modes of Chern-Simons and BTZ black holes with torsion

We study Chern-Simons black holes in d-dimensions and we calculate analytically the quasinormal modes of fermionic perturbations. Also, we consider as background the five-dimensional Chern-Simons black hole with torsion and the BTZ black hole with torsion. We have found that the quasinormal modes depend on the highest power of curvature present in the Chern-Simons theory, such as occurs for the quasinormal modes of scalar perturbations. We also show that the effect of the torsion is to modify the real part of the quasinormal frequencies, which modify the oscillation frequency of the field for the five dimensional case. However, for the BTZ black hole with torsion, the effect is to modify the imaginary part of these frequencies, that is, the relaxation time for the decay of the black hole perturbation. The imaginary part of the quasinormal frequencies is negative which guaranties the stability of these black holes under fermionic field perturbations.

Dirac quasinormal modes for a \(4\)-dimensional Lifshitz black hole

We study the quasinormal modes of fermionic perturbations for an asymptotically Lifshitz black hole in four dimensions with dynamical exponent

QUASINORMAL MODES AND STABILITY ANALYSIS FOR Z = 4 TOPOLOGICAL BLACK HOLE IN 4 + 1-DIMENSIONAL HORAVA–LIFSHITZ GRAVITY

z=2