Triangle Nuclear Theory Colloquium  Bound on Thermalization from Hydrodynamic Fluctuations
December 5,

Speaker(s):
Luca Delacretaz
Interacting systems thermalize. They can do so arbitrarily slowly, but not arbitrarily fast: the time scale necessary for a quantum manybody 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.