Qi, Marvin - University of Chicago

Bound on the emergence of hydrodynamics

Late-time, long-wavelength dynamics of generic many-body interacting quantum systems at finite temperature are described by hydrodynamics. The timescale of the onset of hydrodynamics is naturally interpreted as a local thermalization time. It is natural to expect that thermalization occurs faster when interactions are stronger. We prove that thermalization cannot occur arbitrarily quickly: hydrodynamics can only emerge after a “Planckian” timescale τ_eq ≥ β ℏ.