QED Plasma at Finite Temperature up to Two Loops

Abstract

We study the vacuum polarization tensor of QED (quantum electrodynamics) at high temperatures up to the two loop levels and its effect on the electromagnetic properties of a medium. One loop corrections to QED coupling vanish at low temperatures (T$\leq 10^{10}K$), but they play an important role at high temperature ( T$\geq 10^{10}$ K) to study the behavior of QED medium at these temperatures. At low temperatures ( $T \leq m_e$)higher order loops give a tiny correction due to the coupling of radiation with matter and an overlap of hot photon loop with cold fermion loop contributes to this effect. These higher loop contributions does not affect the convergence of perturbative series, and renormalizability of QED is guaranteed at temperatures around neutrino decoupling. We use the renormalization scheme of QED at finite temperature in real-time formalism to study the dynamically generated mass of photon indicating the plasmon production in such a medium. Temperature dependence of this QED plasma parameters is discussed. We explicitly show that this behavior of a thermal medium exists upto temperatures of a few MeV only. We compare the first order and second order effects upto the 4MeV temperature and demonstrate that the higher order contributions are smaller than the lower order contributions proving the renormalizability of the theory. The lowest order contributions are sufficiently smaller than the original value as well.