Dynamical screening away from equilibrium: hard photon production and   collisional energy loss
  We investigate the production rate for hard real photons and the collisional energy loss in the quark-gluon plasma away from chemical equilibrium. Applying the Hard-Thermal-Loop resummation scheme away from equilibrium, we can show that Landau damping provides dynamical screening for both fermion and boson exchange present in the two quantities. 
R. Baier, M. Dirks, and K. Redlich