From effective actions to actual effects in QED
  The construction of low-energy effective actions in QED for several types of external conditions is reviewed. Emphasis is put on the application of these effective actions to a variety of physical effects which represent a manifestation of vacuum polarization. Soft-photon interactions with external electromagnetic fields and/or a heat bath are described, pair production at finite temperature is discussed, and finally a glance at photon-neutrino interactions is provided. 
Holger Gies (Tubingen U.)