Short-lived lattice quasiparticles for strongly interacting fluids

TL;DR

This paper demonstrates that lattice kinetic theory with short-lived quasiparticles effectively models strongly interacting fluids, revealing a mechanism to achieve low shear viscosity consistent with holographic bounds.

Contribution

It introduces a lattice kinetic theory framework incorporating negative propagation viscosity, enabling simulation of strongly interacting fluids at realistic collisional viscosities.

Findings

Shear viscosity is the sum of collision and propagation contributions.

Propagation viscosity can be negative, reducing total viscosity.

Results align with the AdS-CFT holographic bound.

Abstract

It is shown that lattice kinetic theory based on short-lived quasiparticles proves very effective in simulating the complex dynamics of strongly interacting fluids (SIF). In particular, it is pointed out that the shear viscosity of lattice fluids is the sum of two contributions, one due to the usual interactions between particles (collision viscosity) and the other due to the interaction with the discrete lattice (propagation viscosity). Since the latter is {\it negative}, the sum may turn out to be orders of magnitude smaller than each of the two contributions separately, thus providing a mechanism to access SIF regimes at ordinary values of the collisional viscosity. This concept, as applied to quantum superfluids in one-dimensional optical lattices, is shown to reproduce shear viscosities consistent with the AdS-CFT holographic bound on the viscosity/entropy ratio. This shows that lattice kinetic theory continues to hold for strongly coupled hydrodynamic regimes where continuum kinetic theory may no longer be applicable.