Decay of a charged scalar and Dirac fields in the Kerr-Newman-de Sitter background

We find the quasinormal modes of the charged scalar and Dirac fields in the background of the rotating charged black holes, described by the Kerr-Newman-de Sitter solution. The dependence of the quasinormal spectrum upon the black hole parameters mass M, angular momentum a, charge Q, as well as on values of the \Lambda-term and field charge q is investigated. Special attention is given to the near extremal limit of the black hole charge. In particular, we find that for both scalar and Dirac fields, charged perturbations decay quicker for q>0 and slower for q<0 for values of black holes charge Q less than than some threshold value, which is close to the extremal value of charge and depend on parameters of the black holes.Comment: Phys. Rev. D, in pres

How to tell the shape of a wormhole by its quasinormal modes

Here we shall show how to reconstruct the shape function of a spherically symmetric traversable Lorenzian wormhole near its throat if one knows high frequency quasinormal modes of the wormhole. The wormhole spacetime is given by the Morris-Thorne ansatz. The solution to the inverse problem via fitting of the parameters within the WKB approach is unique for arbitrary tideless wormholes and some wormholes with non-zero tidal effects, but this is not so for arbitrary wormholes. As examples, we reproduce the near throat geometries of the Bronnikov-Ellis and tideless Morris-Thorne metrics by their quasinormal modes at high multipole numbers $\ell$.Comment: 8 pages, revtex4, 1 figure; version accepted for publication in Physics Letters

Quasinormal modes of the charged black hole in Gauss-Bonnet gravity

The d-dimensional string generated gravity models lead to Einstein-Maxwell equations with quadratic order correction term called the Gauss-Bonnet term. We calculate the quasinormal modes for the d-dimensional charged black hole in the framework of this model. The quasinormal spectrum essentially depends upon the Gauss-Bonnet coupling parameter $\alpha$ which is related to the string scale, and is totally different from that for black holes derived from Einstein action. In particular, at large $\alpha$ the quasinormal modes are proportional to $\alpha$, while as $\alpha$ goes to zero the qusinormal modes approach their Schwarzschild values. In contrary to Einstein theory black hole behavior, the damping rate of the charged GB black hole as a function of charge does not contain a chracteristic maximum, but instead the monotonic falling down is observed. In addition, there have been obtained an asymptotic formula for large multipole numbers.Comment: 16 pages, 4 figures, 3 tables; misprints correcte