Far-Away-From-Equilibrium Quantum Critical Conformal Dynamics: Reversibility, Thermalization, and Hydrodynamics

Abstract

Generic far-away-from-equilibrium many-body dynamics usually involve entropy production, and hence are thermodynamically irreversible. Near quantum critical points, an emergent conformal symmetry can impose strong constraints on entropy production rates, and in some cases completely forbid entropy production, which usually occurs for systems that deviate from quantum critical points. In this letter, we illustrate how the vanishing entropy production near a quantum critical point, and at finite temperatures, results in reversible far-away-from-equilibrium dynamics that are otherwise irreversible. Our analysis directly relates the thermalization time scale to the hydrodynamic viscosity near quantum critical points with dynamical critical exponent z = 2. Both controllable reversible and irreversible dynamics can be potentially studied in cold gas experiments.