Short-Lived Lattice Quasiparticles for Strongly Interacting Fluids

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 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.

Kinetic approach to relativistic dissipation

“…A further intriguing question pertains to the relevance of this analysis to strongly-interacting holographic fluids obeying the AdS-CFT bound [39]. Indeed, while such fluids are believed to lack a kinetic description altogether, since quasi-particles are too short-lived to carry any physical relevance, they are still amenable to a lattice kinetic description, reaching down to values of η/s well below the AdS-CFT bound [40,41]. Work to explore the significance of the AdS-CFT bounds in lattice fluids is currently underway.…”