Room 6420,ITP new Building/理论物理所新楼6420报告厅

Heisenberg and Euler found the one-loop affective action in a constant electromagnetic field soon after Dirac theory was discovered, and Schwinger introduced the proper-time integral representation of QED action and showed that strong electric fields could spontaneously produce electron-positron pairs, the so-called (Sauter-) Schwinger pair production. With the discovery of neutron stars and/or magnetars, cosmic scale magnetic field and the advent of (ultra-) intense lasers via the chirped pulsed amplification (CPA) technology by Mourou and Strickland, physics in strong electromagnetic fields has been emerging as a new science in the 21st century as much as gravitational waves from strong gravity sources. In the first talk, theoretical aspects of strong field QED will be explained from vacuum polarization to Schwinger pair production to nonlinear Compton scattering.  An electron or charges in a uniform electromagnetic field is described by the dressed propagator, which is equivalent to a free electron interacting with arbitrary number of photons, and which leads to the one-loop effective action. After briefly explaining a few well known methods for finding one-loop effective action, the gamma-function regularization method is introduced, which is based on Schwinger-DeWitt variational principle in the in-out formalism, and Schwinger pair production is discussed in the in-out formalism. Vacuum birefringence, light-light scattering, and nonlinear Compton scattering are discussed in strong electromagnetic fields. Finally, the gamma-function regularization is applied to find the one-loop effective action in a uniform electric and/or magnetic field in (anti-) de Sitter space, and Schwinger pair production is discussed in (anti-) de Sitter space and charged black holes.