From extended phase space dynamics to fluid theory

TL;DR

This paper develops a fluid theory for spin-1/2 particles from an extended kinetic model, highlighting the importance of a pressure-like term in the spin density evolution and demonstrating its significance in a linear mode analysis.

Contribution

It introduces a novel fluid model derived from a spin-projected kinetic framework, incorporating a pressure-like term in the spin dynamics.

Findings

The pressure-like term significantly affects the spin evolution.

The model reproduces a known linear mode in spin kinetic theory.

The extended kinetic approach provides new insights into spin fluid behavior.

Abstract

We derive a fluid theory for spin-1/2 particles starting from an extended kinetic model based on a spin-projected density matrix formalism. The evolution equation for the spin density is found to contain a pressure-like term. We give an example where this term is important by looking at a linear mode previously found in a spin kinetic model.