Degeneracies of discrete and continuum states with the Dirac sea in the pair-creation process

By solving the quantum field theoretical Dirac and Klein-Gordon equations numerically we analyze the different roles of discrete and continuum states for the pair-creation process from the vacuum. If this process is solely induced by discrete states that have become degenerate with the negative energy continuum, the complex scaling method can predict the time scales associated with the bosonic as well as fermionic growth of the particle yield. We show that for bosons the long-time exponential growth behavior is not affected by additional continuum-continuum degeneracies, while for fermions they characterize the asymptotic (linear) growth. We illustrate the impact of these degeneracies on the temporally resolved energy and spatial distributions of the created particles.