A Note on Coadjoint Orbits for Multifermion Systems

TL;DR

This paper explores the coadjoint orbit action for multifermion systems, providing a parametrization that enables approximations around the Fermi surface and connecting to existing models.

Contribution

It introduces a parametrization of the coadjoint orbit variables that simplifies approximations and relates to prior actions used in the literature.

Findings

Provides a parametrization facilitating Fermi surface expansions

Connects coadjoint orbit actions to previously used models

Discusses phase space functions with star-products and truncations

Abstract

The coadjoint orbit action for a multifermion system, as an exact description of its dynamics, is considered. A parametrization of the variables involved is given which facilitates the approximation of this by another coadjoint orbit action suitable for expansions around the Fermi surface, recovering various actions which have been used in previous literature. The presentation of this in terms of functions on phase space with star-products as well as further truncations are briefly considered.