Enhanced electron-positron pair creation by dynamically assisted combinational fields

Enhanced electron-positron pair creation by dynamically assisted combinational fields is investigated based on the quantum Vlasov equation. We propose four kinds of electric fields of either addition or multiplication of sinusoid or/and exponent function and make some comparisons for pair number density with each other. It is found that the high frequency assisted field will enhance pair production significantly. For each combinational field there is an optimal frequency ratio of fast time varying field to slow one so that the pair production number density can be increased very much over a few orders of magnitude. We also find an optimal combined field that is the multiplication of a slow varying exponent field with a rapid varying sinusoid one. It keeps advantages of two fields, i.e. the exponent field has a stationary property and the sinusoid field has a high pair production number density.