Particle Creation in Kaluza-Klein Cosmology

TL;DR

This paper calculates particle creation in higher-dimensional cosmological models, revealing thermal distributions and conditions under which particles are produced or suppressed, with implications for early universe physics.

Contribution

It provides exact calculations of particle number in Kaluza-Klein cosmologies, showing thermal behavior and momentum-dependent effects not previously detailed.

Findings

Particle distribution shows thermal behavior at high momentum

Particle number can be independent of extra-dimensional momentum

A cutoff momentum may prevent particle production below a certain threshold

Abstract

We exactly calculate the particle number $N$ of scalar fields which are created from an initial vacuum in certain higher-dimensional cosmological models. The spacetimes in these models are the four-dimensional Chitre-Hartle or radiation-dominated universe with extra spaces which are static or power-law contracting. Except for some models in which no particles could be produced, the distribution of created particles shows a thermal behavior, at least in the limit of high three-dimensional "momentum" $k$. In some models, $N$ does not depend on the magnitude of the extra-dimensional "momentum" $k_c$ if $k_c$ is nonvanishing. A cutoff momentum $k_c$ may emerge in some models, and particles with $k\le k_c$ could not be produced. We also discuss these results.