Showing papers by "Ayan Mukhopadhyay published in 2012"

Holographic spectral function in nonequilibrium states

Abstract: We develop holographic prescriptions for obtaining spectral functions in nonequilibrium states and space-time dependent nonequilibrium shifts in the energy and spin of quasiparticle-like excitations. We reproduce strongly coupled versions of aspects of nonequilibrium dynamics of Fermi surfaces in Landau's Fermi-liquid theory. We find that the incoming wave boundary condition at the horizon does not suffice to obtain a well-defined perturbative expansion for nonequilibrium observables. Our prescription, based on analysis of regularity at the horizon, allows such a perturbative expansion to be achieved nevertheless and can be precisely formulated in a universal manner independent of the nonequilibrium state, provided the state thermalizes. We also find that the nonequilibrium spectral function furnishes information about the relaxation modes of the system. Along the way, we argue that in a typical nonsupersymmetric theory with a gravity dual, there may exist a window of temperature and chemical potential at large $N$, in which a generic nonequilibrium state can be characterized by just a finitely few operators with low scaling dimensions, even far away from the hydrodynamic limit.

Phenomenology of Irreversible Processes from Gravity

Abstract: Department of Physics and Astronomy, University of Southern CaliforniaLos Angeles, California 90089-0484,USAE-mail:ramaiyer@usc.eduWe propose that the space-time evolution of strongly coupled matter formed by ultra-relativisticheavy ion collisions can be modelled by phenomenological equations involving the energy-momentum tensor and conserved currents alone. These equations can describe the late stage oflocal thermal and chemical equilibration of the matter formed after collisions, and its subsequenttransition to hydrodynamic expansion in an unified framewor k. The full set of equations includelocal energy, momentum and charge conservation; but also additional equations for evolution ofnon-equilibrium variables. These equations with precisely determined phenomenological param-eters can be obtained by the AdS/CFT correspondence. On the gravity side of this correspon-dence, for vanishing chemical potentials, these phenomenological equations give all solutions ofpure gravity in AdS which have regular future horizons. We also discuss field-theoretic groundsfor validity of these phenomenological equations.The 2011 Europhysics Conference on High Energy Physics-HEP2011,July 21-27, 2011Grenoble, RhAt’ne-Alpes France