Ward Identities in Non-equilibrium QED

TL;DR

This paper verifies the QED Ward identity for two- and three-point functions in non-equilibrium conditions using the Keldysh formalism and HTL effective propagators, confirming theoretical consistency.

Contribution

It demonstrates the validity of the Ward identity in non-equilibrium QED at the HTL level using real-time finite temperature field theory.

Findings

Ward identity holds for two- and three-point functions in non-equilibrium QED

Verification performed at one-loop level with HTL effective propagators

Consistent with theoretical expectations in non-equilibrium conditions

Abstract

We verify the QED Ward identity for the two- and three -point functions at non-equilibrium in the HTL limit. We use the Keldysh formalism of real time finite temperature field theory. We obtain an identity of the same form as the Ward identity for a set of one loop self-energy and one loop three-point vertex diagrams which are constructed from HTL effective propagators and vertices.