Cancellation of unphysical gauge and ghost degrees of freedom in backreaction

TL;DR

This paper investigates the U(1) Higgs model in dynamic backgrounds, demonstrating that unphysical particles generated do not affect the background fields, thus clarifying gauge and ghost degree of freedom cancellations.

Contribution

It shows that unphysical gauge and ghost degrees of freedom do not contribute to backreaction in the U(1) Higgs model with spacetime-dependent backgrounds.

Findings

Unphysical particles are produced but do not influence background fields.

Gauge and ghost degrees of freedom cancel out in backreaction calculations.

Particle creation occurs due to background field time-dependence.

Abstract

We study the U(1) Higgs model in spacetime-dependent background fields (a background metric and a background scalar field). Particle creation can occur because of the time-dependence of these background fields. In gauge theories, there is a unphysical sector and consequently unphysical particles may be produced. However, it is shown that produced unphysical particles have no contribution to backreaction to background fields.