# Equilibration of Quasi-One-Dimensional Fermi Gases

## TL;DR

This paper investigates how multi-channel one-dimensional Fermi gases relax to equilibrium at low temperatures, revealing unique scattering processes and calculating their bulk viscosity to understand their hydrodynamic behavior.

## Contribution

It provides a detailed analysis of relaxation mechanisms and bulk viscosity in two-channel Fermi gases, highlighting an unexpected conservation law affecting their dynamics.

## Key findings

- Identification of dominant scattering processes obeying a new conservation law
- Calculation of bulk viscosity for two-channel Fermi gases
- Analysis of eigenmodes of the linearized collision integral

## Abstract

One-dimensional systems often possess multiple channels or bands arising from the excitation of transverse degrees of freedom. In the present work, we study the specific processes that dominate the equilibration of multi-channel Fermi gases at low temperatures. Focusing on the case of two channels, we perform an analysis of the relaxation properties of these systems by studying the spectrum and eigenmodes of the linearized collision integral. As an application of this analysis, a detailed calculation of the bulk viscosity is presented. The dominant scattering processes obey an unexpected conservation law which is likely to affect the hydrodynamic behavior of these systems.