Narrow Results

We study the theory of interaction between charged scalar field and Maxwell field in de Sitter background. Solving the equation of interacting fields, we define the in–out fields as asymptotic free fields and construct the reduction formalism for scalar field. Then we derive the perturbation expansion of the scattering operator. The first-order transition amplitudes corresponding to particle production from de Sitter vacuum and pair production in an external field are analyzed. We show that all these effects are important only in strong gravitational fields and vanish in the flat limit.

Fermion production in external electric field on de Sitter expanding universe is analyzed. The amplitude and probability of pair production are computed. We obtain from our calculations that the modulus of the momentum is no longer conserved. The rate of pair production in an electric field is found to be important in the early universe when the expansion factor was large comparatively with the particle mass. A computation of the total probability is presented in a particular case and the result proves to be nonvanishing only in strong gravitational fields.