Symmetry restoration, Tunnelling and the Null Energy Condition

TL;DR

This paper explores how tunnelling between degenerate vacua at finite temperature affects vacuum energy, leading to violations of the Null Energy Condition through a detailed analysis of saddle points in quantum field theory.

Contribution

It introduces a comprehensive description of tunnelling effects at finite temperature, highlighting the dynamical violation of the Null Energy Condition due to non-extensive vacuum energy.

Findings

Finite volume tunnelling influences vacuum energy.

Dynamical Null Energy Condition violation occurs at low temperatures.

Effective theory reveals competition of saddle points in partition function.

Abstract

A finite volume allows tunnelling between degenerate vacua in Quantum Field Theory, and leads to remarkable energetic features, arising from the competition of different saddle points in the partition function. We describe this competition for finite temperature at equilibrium, taking into account both static and (Euclidean) time-dependent saddle points. The effective theory for the homogeneous order parameter yields a non-extensive vacuum energy at low temperatures, implying a dynamical violation of the Null Energy Condition.