Nonperturbative QED Effective Action at Finite Temperature

Understand

We advance a novel method for the finite-temperature effective action for nonequilibrium quantum fields and find the QED effective action in time-dependent electric fields, where charged pairs evolve out of equilibrium.

• The imaginary part of the effective action consists of thermal loops of the Fermi-Dirac or Bose-Einstein distribution for the initial thermal ensemble weighted with factors for vacuum fluctuations.
• And the real part of the effective action is determined by the mean number of produced pairs, vacuum polarization, and thermal distribution.
• The mean number of produced pairs is equal to twice the imaginary part.