# Chiral Kinetic Theory from Effective Field Theory Revisited

## TL;DR

This paper compares two approaches to deriving the chiral kinetic equation, revealing differences in high-order terms but establishing their equivalence in describing chiral fermion dynamics.

## Contribution

It demonstrates that differences between effective field theory and field theory derivations are due to choice of degrees of freedom, and shows their equivalence in describing chiral fermions.

## Key findings

- Differences in high-order terms in $O(1/u)$ expansion.
- Equivalence of the two approaches in describing chiral fermion dynamics.
- Reparametrization transformations explain the differences.

## Abstract

We revisit the chiral kinetic equation from high density effective theory approach, finding a chiral kinetic equation differs from counterpart derived from field theory in high order terms in the $O(1/\mu)$ expansion, but in agreement with the equation derived in on-shell effective field theory upon identification of cutoff. By using reparametrization transformation properties of the effective theory, we show that the difference in kinetic equations from two approaches are in fact expected. It is simply due to different choices of degree of freedom by effective theory and field theory. We also show that they give equivalent description of the dynamics of chiral fermions.