Speaker
Description
We examine the length scales usually associated with the applicability of hydrodynamics as an effective theory in the light of the observation of hydrodynamic behavior in small systems. We argue that the explanation of such behavior might reside in the requirement of local equivalence between fluctuations and dissipative dynamics. In a way somewhat analogous to the equivalence of gravity and acceleration in general relativity, this leads to a theory which is generally covariant and non-perturbative in fluctuations. We argue that the scale separation in this theory is very different from the Knudsen number, thus explaining how strongly coupled systems with just a few degrees of freedom are characterized by an ensemble of trajectories whose average could be close to that of an ideal fluid. Based on https://arxiv.org/abs/2504.17152