Triangle Nuclear Theory Colloquium - Bound on Thermalization from Hydrodynamic Fluctuations

Interacting systems thermalize. They can do so arbitrarily slowly, but
not arbitrarily fast: the time scale necessary for a quantum many-body
system to reach local thermal equilibrium has been conjectured to be
bounded below by the Planckian time, \hbar/T. I will show that
consistency of hydrodynamics (or diffusion), which generically emerges
at late times, implies that this local equilibration time indeed has a
lower bound. The key tool is the derivation of universal corrections to
diffusion at intermediate times using EFT techniques: when these
corrections are large the system cannot have thermalized. For the
special case of CFTs, combining this argument with scale invariance
allows one to prove the conjectured Planckian bound. I will also discuss
spin chains, where the knowledge of these universal corrections to
diffusion can allow for precision tests of thermalization, and a more
accurate identification of a thermalizing system's dissipative
universality class with limited numerical resources.

NOTE: Light Refreshments will be served at 3:00 PM.