Particle Creation in Kaluza-Klein Cosmology
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≤
k
c
could not be produced. We also discuss these results.