Seminar
Speaker
Debangshu Mukherjee ( Chennai Mathematical Institute, Chennai)
Date & Time
10 February 2017, 11:00 to 12:00
Venue
Nambu Discussion Room (Right), ICTS Campus, Bangalore
Abstract
Motivated by the analysis of Kovtun, Son and Starinets, we study the diffusion constant for theories with Lifshitz and hyperscaling violating exponents z and Θ. We study shear  gravitational perturbations in the near-horizon region imposing certain self-consistent  approximations on a suitably defined stretched horizon. This is effectively done by compactifying  the hyperscaling violating Lifshitz theory along a spatial direction thus mapping shear gravitational perturbations to gauge field perturbations in the compactified theory. Through appropriately defined currents on the stretched horizon, we set up a diffusion equation and hence calculate the shear diffusion constant for these hyperscaling violating theories. It is observed for a certain class of hyperscaling violating theories i.e when z<4-Θ, we see the diffusion constant scales as a power law with respect to temperature suggesting universal behaviour in relation to the viscosity bound. When z≥4-Θ, diffusion constant scales logarithmically with temperature, and seems to violate the KSS bound  possibly suggesting a breakdown of our analysis.