On the energy-momentum spectrum of a homogeneous Fermi gas

TL;DR

This paper investigates the energy-momentum spectrum of a homogeneous Fermi gas, suggesting it features a positive energy gap and critical velocity, consistent with quasiparticle effective models.

Contribution

It provides theoretical insights into the spectral properties of an interacting Fermi gas in the thermodynamic limit, emphasizing the role of quasiparticles.

Findings

Spectrum likely has a positive energy gap.

Spectrum exhibits a positive critical velocity.

Supports quasiparticle model consistency.

Abstract

We consider translation invariant quantum systems in thermodynamic limit. We argue that their energy-momentum spectra should have shapes consistent with effective models involving quasiparticles. Our main example is second quantized homogeneous interacting Fermi gas in a large cubic box with periodic boundary conditions, at zero temperature. We expect that its energy-momentum spectrum has a positive energy gap and a positive critical velocity.