Viscosity to entropy ratio at extremality (2009)
Chakrabarti, Sayan K., Jain, Sachin, Mukherji, Sudipta
Assuming gauge theory realization at the boundary, we show that the viscosity to entropy ratio is 1/(4 pi) where the bulk is represented by a large class of extremal black holes in anti-de Sitter...
A new approach to modified-gravity models (2009)
Chakrabarti, Sayan K., Saridakis, Emmanuel N., Sen, Anjan A.
We investigate f(R)-gravity models performing the ADM-slicing of standard General Relativity. We extract the static, spherically-symmetric vacuum solutions in the general case, which correspond to...
Scalar field dynamics in warped AdS_3 black hole background (2009)
Chakrabarti, Sayan K., Giri, Pulak Ranjan, Gupta, Kumar S.
We study the normal modes of a scalar field in the background of a warped AdS_3 black hole which arises in topologically massive gravity. The explicit forms of the normal mode eigenvalues are found...
A comparative study of Dirac quasinormal modes of charged black holes in higher dimensions (2008)
In this work we study the Dirac quasinormal modes of higher dimensional charged black holes. Higher dimensional Reissner-N\"{o}rdstrom type black holes as well as charged black holes in Einstein...
Normal mode analysis for scalar fields in BTZ black hole background (2008)
Chakrabarti, Sayan K, Giri, Pulak Ranjan, Gupta, Kumar S.
We analyze the possibility of inequivalent boundary conditions for a scalar field propagating in the BTZ black hole space-time. We find that for certain ranges of the black hole parameters, the...
Universal near-horizon conformal structure and black hole entropy (2007)
Chakrabarti, Sayan K., Gupta, Kumar S., Sen, Siddhartha
It is shown that a massless scalar probe reveals a universal near-horizon conformal structure for a wide class of black holes, including the BTZ. The central charge of the corresponding Virasoro...
We obtain the quasinormal modes for tensor perturbations of Gauss-Bonnet (GB) black holes in $d=5, 7, 8$ dimensions and vector perturbations in $d = 5, 6, 7$ and 8 dimensions using third order WKB...
Chakrabarti, Sayan K., Gupta, Kumar S.
We obtain an analytic expression for the highly damped asymptotic quasinormal mode frequencies of the $d\geq 5$-dimensional Schwarzschild black hole modified by the Gauss-Bonnet term, which appears...