Path integral approach to particle production in a spatially-flat Robertson-Walker spacetime with cosmic scale factors a(t) = a0cosh(αt) and a(t) = a0sin(αt)

Abstract

Pair production of free scalar particles in spatially-flat Robertson-Walker spacetime described by the metric
ds² = −dt² + a(t)[dx₁² + dx₂² +dx₃²]
with cosmic scale factors a(t) = a₀cosh(αt) and a(t) = a₀sin(αt) was investigated. These cosmic scale factors correspond to the "open" universe and "closed" universe models, respectively. (The description is based on the behavior of expansion and not on the geometry of spacetime).