Quasinormal modes of Schwarzschild-anti-de Sitter black holes: Electromagnetic and gravitational perturbations - art. no. 084017

We study the quasinormal modes (QNM.) of electromagnetic and gravitational perturbations of a Schwarzchild black hole in an asymptotically anti-de Sit ter (AdS) spacetime. Some of the electromagnetic modes do not oscillate; th ey only decay, since they have pure imaginary frequencies. The gravitationa l modes show peculiar features: the odd and even gravitational perturbation s no longer have the same characteristic quasinormal frequencies. There is a special mode for odd perturbations whose behavior differs completely from the usual one in scalar and electromagnetic perturbations in AdS spacetime . but has a similar behavior to the Schwarzschild black hole in an asymptot ically flat spacetime: the imaginary part of the frequency goes as l/r(+), where r(+) is the horizon radius. We also investigate the small black-hole limit showing that the imaginary part of the frequency goes as r(+)(2). The se results are important to the AdS/CFT conjecture since, according to it, the QNM's describe the approach to equilibrium in the conformal field theor y.