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Roman Konoplya (Germany),
"Perturbations, quasinormal modes and stability of black holes in Einstein-Gauss-Bonnet and Lovelock theories"
Abstract: Perturbations of asymptotically anti-de Sitter black holes and branes play an important role in the holographic description of strongly coupled systems, such as quark-gluon plasmas.
Adding of higher curvature corrections to the Einstein action may help to describe the intermediate coupling regime, thereby making a bridge between the strong coupling and the kinetic theory.
Within this context we show that at some values of the parameters black holes and branes in the Einstein-Gauss-Bonnet gravity and its Lovelock generalization suffer from a catastrophic instability,
which is accompanied by the lack of hyperbolicity of the master perturbation equation. We rigorously investigate the parametric region of this instability and show that some previous results,
for example holographic description of superfluidity is highly questionable because of the instability.
In addition, we shall show that the asymptotically flat black holes in the Einstein-Gauss-Bonnet gravity violate the correspondence between the quasinormal modes and the parameters
of circular null geodesics formulated by V. Cardoso et. al [Phys. Rev. D 79, 064016 (2009)]. Nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits.

The talk is based on:
R. Konoplya, Z. Stuchlik, Phys.Lett. B771 (2017) 597;
P. Gonzales, R. Konoplya, Y. Vasquez, Phys.Rev. D95 (2017), 124012;
R. Konoplya, A. Zhidenko, Phys.Rev. D95 (2017), 104005; JHEP 1709 (2017) 139.


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