a subgroup x of a group g is said to be an h -subgroup if n_g(x) ∩ x^g ≤ x for each element g belonging to g. in [m. bianchi e. a., on finite soluble groups in which normality is a transitive relation, j. group theory, 3 (2000), 147–156] the authors showed that finite groups in which every subgroup has the h -property are exactly soluble groups in which normality is a transitive relation. here ...

We initiate the study of equilibration rates of strongly coupled quark-gluon plasmas in the absence of conformal symmetry. We primarily consider a supersymmetric mass deformation within N=2^{*} gauge theory and use holography to compute quasinormal modes of a variety of scalar operators, as well as the energy-momentum tensor. In each case, the lowest quasinormal frequency, which provides an app...

In this work we study the Dirac quasinormal modes of higher dimensional charged black holes. Higher dimensional Reissner-Nordström type black holes as well as charged black holes in Einstein Gauss-Bonnet theories are studied for Fermionic perturbations using WKB methods. A comparative study of the quasinormal modes in the two different theories of gravity has been performed. The beahviour of th...

We use the Lorentzian AdS/CFT prescription to find the poles of the retarded thermal Green’s functions of N = 4 SU(N) SYM theory in the limit of large N and large ’t Hooft coupling. In the process, we propose a natural definition for quasinormal modes in an asymptotically AdS spacetime, with boundary conditions dictated by the AdS/CFT correspondence. The corresponding frequencies determine the ...

The purpose of the current Letter is to give some relations between gravitational lensing in the strong-deflection limit and the frequencies of the quasinormal modes of spherically symmetric, asymptotically flat black holes. On the one side, the relations obtained can give a physical interpretation of the strong-deflection limit parameters. On the other side, they also give an alternative metho...

We discuss the relation between bulk de Sitter three-dimensional spacetime and the corresponding conformal field theory at the boundary, in the framework of the exact quasinormal mode spectrum. We show that the quasinormal mode spectrum corresponds exactly to the spectrum of thermal excitations of Conformal Field Theory at the past boundary I, together with the spectrum of a Conformal Field The...

The spectrum of Hawking radiation by quantum fields in the curved spacetime is continuous, so the explanation of Hawking radiation using quasinormal modes can be suspected to be impossible. We find that quasinormal modes do not explain the relation between the state observed in a region far away from a black hole and the short distance behavior of the state on the horizon. Loop quantum gravity ...

We point out an elementary thermodynamics fact that whenever the specific heat of a system is negative, the speed of sound in such a media is imaginary. The latter observation presents a proof of Gubser-Mitra conjecture on the relation between dynamical and thermodynamic instabilities for gravitational backgrounds with a translationary invariant horizon, provided such geometries can be interpre...

Using the Pöshl-Teller approximation, we evaluate the neutrino quasinormal modes (QNMs) of a Kerr-Newman-de Sitter black hole. The result shows that for a Kerr-Newman-de Sitter black hole, massless neutrino perturbation of large Λ, positive m and small value of n will decay slowly. PACS number(s): 04.70.-s, 04.50.+h, 11.15.-q, 11.25.Hf e-mail: ygshen @center.shao.ac.cn