Schwinger Pair Production at Finite Temperature in QED
  We use the evolution operator method to find the Schwinger pair-production rate at finite temperature in scalar and spinor QED by counting the vacuum production, the induced production and the stimulated annihilation from the initial ensemble. It is shown that the pair-production rate for each state is factorized into the mean number at zero temperature and the initial thermal distribution for bosons and fermions. 
Sang Pyo Kim, Hyun Kyu Lee, and Yongsung Yoon