Andrei Starinets

Abstract:

We study the hydrodynamics of the high-energy phase of Little String Theory. The poles of the retarded two-point function of the stress energy tensor contain information about the speed of sound and the kinetic coefficients, such as shear and bulk viscosity. We compute this two-point function in the dual string theory and analytically continue it to lorentzian signature. We perform an independent check of our results by the lorentzian supergravity calculation in the background of non-extremal NS5-branes. The speed of sound vanishes at the Hagedorn temperature. The ratio of shear viscosity to entropy density is equal to the universal value 1/4π and does not receive α′ corrections. The ratio of bulk viscosity to entropy density equals 1/10π. We also compute the R-charge diffusion constant. In addition to the hydrodynamic singularities, the correlators have an infinite series of finite-gap poles, and a massless pole with zero attenuation. © SISSA 2005.

Abstract:

Gauge theory-gravity duality predicts that the shear viscosity of N = 4 supersymmetric SU(Nc) Yang-Mills plasma at temperature T in the limit of large N c and large 't Hooft coupling gYM2Nc is independent of the coupling and equals to πNc2T3 /8. In this paper, we compute the leading correction to the shear viscosity in inverse powers of 't Hooft coupling using the α′-corrected low-energy effective action of type IIB string theory. We also find the correction to the ratio of shear viscosity to the volume entropy density (equal to 1/4π in the limit of infinite coupling). The correction to 1/4π scales as (gYM2Nc) -3/2 with a positive coefficient. © 2004 Elsevier B.V. All rights reserved.