Off-shell hydrodynamics from holography

Understand

We outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual.

• As a first step, in this paper we restrict to systems with a non-dissipative horizon.
• By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces.
• At zeroth order, this action reduces to that proposed by Dubovsky et al.