Particle production in expanding spacetime (Q1604880)

The authors describe the application of the CWKB method -- complex time WKB approximation -- to the long standing problem of particle production in the expanding Universe. Using this method they analyze the adiabatic and non-adiabatic transition. One of the conclusions says that there exists a topological characteristic of the spacetime responsible for of the emergence the thermal radiation. It divides the spacetime into the Euclidean and non-Euclidean region. In this approach the Euclidean vacuum fluctuation is a main source of thermal particle production. The authors discuss also the dependence of particle production on the behavior of the scale factor at early times.