Effect of electromagnetic fields on the creation of scalar particles in   a flat Robertson-Walker space-time
  The influence of electromagnetic fields on the creation of scalar particles from vacuum in a flat Robertson-Walker space-time is studied. The Klein Gordon equation with varying electric field and constant magnetic one is solved. The Bogoliubov transformation method is applied to calculate the pair creation probability and the number density of created particles. It is shown that the electric field amplifies the creation of scalar particles while the magnetic field minimizes it. 
S. Haouat and R. Chekireb
hep-th gr-qc