Iberian Strings Meetings 

19/01/2021, 11:00 — 11:30 — Online
Matteo Baggioli, Jiao Tong University Shanghai

How small hydrodynamics can go

Numerous experimental and theoretical results in liquids and plasmas suggest the presence of a critical momentum at which the shear diffusion mode collides with a non-hydrodynamic relaxation mode, giving rise to propagating shear waves. This phenomenon, labelled as $k$-gap, could explain the surprising identification of a low frequency elastic behavior in confined liquids. More recently, a formal study of the perturbative hydrodynamic expansion showed that critical points in complex space, such as the aforementioned $k$-gap, determine the radius of convergence of linear hydrodynamics, its regime of applicability. In this talk, we combine the two new concepts and we study the radius of convergence of linear hydrodynamics in real liquids by using several data from simulations and experiments. We generically show that the radius of convergence increases with temperature and it surprisingly decreases with the interactions coupling. More importantly, we find that such radius is universally set by the characteristic interatomic distance of the liquid, which provides a natural microscopic bound. We finally compare our results with those from holographic theories.

See also

talk_baggioli.pdf