Schwinger mechanism with time-dependent electric fields

The Schwinger mechanism, the vacuum pair production in the presence of strong electric fields, is one of the most remarkable predictions of strong-field QED. For a constant electric field, it was established by Schwinger in 1951 that the vacuum pair production is driven by quantum tunneling and the resulting production number is non-perturbatively suppressed. The constant electric field configuration is, however, too idealistic. Strong electric fields that may be realized in actual physical situations (e.g., intense lasers and heavy-ion collisions) must be time- (as well as space-) dependent. Thus, we need to go beyond Schwinger's constant-field result.
In this talk, I discuss how time-dependence affects the vacuum pair production. In particular, I plan to discuss (1) the interplay between non-perturbative and perturbative pair production mechanisms and show that the widely-used Keldysh parameter is not the only parameter that controls the interplay [1, 2]; (2) dynamically assisted Schwinger mechanism and Franz-Keldysh effect in strong-field QED based on the perturbation theory in the Furry picture [3,4].

Refs:
[1] HT, H. Fujii, K. Itakura, PRD 90, 014039 (2014)
[2] HT, T. Fujimori, T. Misumi, M. Nitta, N. Sakai, JHEP 03, 082 (2021)
[3] HT, PRD 99, 056006 (2019)
[4] X.-G. Huang, HT, PRD 100, 016013 (2019)