Renormalisation of out-of-equilibrium quantum fields

TL;DR

This paper investigates the renormalisation process for out-of-equilibrium quantum fields using the 2PI effective action, demonstrating that equilibrium counterterms can also renormalise time evolution with suitable initial conditions.

Contribution

It shows that with appropriate initial conditions, the same counterterms used in equilibrium are sufficient for renormalising the non-equilibrium dynamics in the 2PI framework.

Findings

Counterterms from equilibrium suffice for out-of-equilibrium renormalisation.

Improvement over Gaussian initial conditions by ensuring a continuum limit.

Enhanced understanding of initial condition effects on quantum field evolution.

Abstract

We consider the initial value problem and its renormalisation in the framework of the two-particle-irreducible (2PI) effective action. We argue that in the case of appropriately chosen self-consistent initial conditions, the counterterms needed to renormalise the system in equilibrium are also sufficient to renormalise its time evolution. In this way we improve on Gaussian initial conditions which have the disadvantage of generically not showing a continuum limit. For a more detailed discussion see arXiv:0809.0496.