# Viscous dissipation in a gas of one-dimensional fermions with generic dispersion

## TL;DR

This paper investigates how lattice effects, interactions, and non-equilibrium conditions influence the bulk viscosity of one-dimensional Fermi gases with various energy-momentum dispersions, extending classical results to more complex quantum systems.

## Contribution

It provides a comprehensive analysis of bulk viscosity in 1D Fermi gases with generic dispersions, including effects of lattice, interactions, and non-equilibrium regimes, introducing three bulk viscosities for the latter case.

## Key findings

- Lattice effects can significantly alter bulk viscosity in tight-binding models.
- Weak interactions modify the bulk viscosity in predictable ways.
- Non-equilibrium regimes require three distinct bulk viscosities to describe dissipation.

## Abstract

A well-known feature of the classical monoatomic gas is that its bulk viscosity is strongly suppressed because the single-particle dispersion is quadratic. On the other hand, in condensed matter systems the effective single-particle dispersion is altered by lattice effects and interactions. In this work, we study the bulk viscosity of one-dimensional Fermi gases with generic energy-momentum dispersion relations. As an application, viscous dissipation arising from lattice effects is analyzed for the tight-binding model. In addition, we investigate how weak interactions affect the bulk viscosity. Finally, we discuss viscous dissipation in the regime in which the Fermi gas is not fully equilibrated, as can occur when the system is driven at frequencies that exceed the rate of fermion backscattering. In this case, the Fermi gas is described by three bulk viscosities, which we obtain for a generic single-particle dispersion.