We find quasinormal modes of near extremal black branes by solving a singular boundary value problem for the Heun equation. The corresponding eigenvalues determine the dispersion law for the collective excitations in the dual strongly coupled N = 4 SYM at finite temperature. In memory of Aleksandr Sergeevich Vshivtsev

In this talk we review different applications of quasinormal modes to black hole physics, string theory and thermalisation in quantum field theory. In particular, we describe the the relation between quasi normal modes of AdS black holes and the time scale for thermalisation in strongly coupled, large N conformal field theory. We also discuss the problem of unitarity within this approach.

We calculate the quasinormal modes and associated frequencies of the Bañados, Zanelli and Teitelboim (BTZ) non-rotating black hole. This black hole lives in 2+1-dimensions in an asymptotically anti-de Sitter spacetime. We obtain exact results for the wavefunction and quasi normal frequencies of scalar, electromagnetic and Weyl (neutrino) perturbations. E-mail: [email protected] E-mail:...

We expound in detail a method frequently used to reduce the Dirac equation in D-dimensional (D ≥ 4) spherically symmetric spacetimes to a pair of coupled partial differential equations in two variables. As a simple application of these results we exactly calculate the quasinormal frequencies of the uncharged Dirac field propagating in the D-dimensional Nariai spacetime.

Using the monodromy method we calculate the asymptotic quasinormal (QN) frequencies of an electromagnetic field moving in D-dimensional Schwarzschild and Schwarzschild de Sitter (SdS) black holes (D ≥ 4). For theD-dimensional Schwarzschild anti-de Sitter (SadS) black hole we also compute these frequencies with a similar method. Moreover, we calculate the electromagnetic normal modes of the D-di...

In this note, we obtain some criteria for p-supersolvablity of a finite group and extend some known results concerning weakly S-semipermutable subgroups. Mathematics Subject Classification (2010). 20D10.

we discuss whether finiteness properties of a profinite group $g$ can be deduced from the coefficients of the probabilisticzeta function $p_g(s)$. in particular we prove that if $p_g(s)$ is rational and all but finitely many non abelian composition factors of $g$ are isomorphic to $psl(2,p)$ for some prime $p$, then $g$ contains only finitely many maximal subgroups.

In this paper, we have focused to study convex $L$-subgroups of an $L$-ordered group. First, we introduce the concept of a convex $L$-subgroup and a convex $L$-lattice subgroup of an $L$-ordered group and give some examples. Then we find some properties and use them to construct convex $L$-subgroup generated by a subset $S$ of an $L$-ordered group $G$ . Also, we generalize a well known result a...

We study the definability of certain subgroups of a group G that does not have the independence property. If a (type) definable subset X of an elementary extension G of G has property P , we call its trace X∩G over G an externally (type) definable P set. We show the following. Centralisers of subsets of G are externally definable subgroups. Cores of externally definable subgroups and iterated c...

In this paper, we calculated the quasinormal modes (QNMs) of a charged non-commutative black hole in scalar, electromagnetic and gravitational fields by three methods. We gave influence parameter $\theta$ charge $Q$ on QNMs different fields. Thereafter, shadow radius provided valid range using constraints $\text{M87}^{\ast}$ $\text{Sgr A}^{\ast}$ from Event Horizon Telescope (EHT). addition, es...