Media Effects Of Toy Models At Hard Thermal Loop Approximation

The thesis can be divided into three parts. The first part is a brief review of Finite-Temperature Field Theory. In the second part, the deduced self-energy in φ63 theory is derived at hard thermal loop approximation. Then we calculate the effective mass and damping rate, and also show that there is thermal instability above a critical temperature Tc. The effective mass and damping rate are proportional to gT and gT respectively. In the third part, the Feynman rules of scalar QED is derived clearly, followed by photon self-energy and scalar self-energy. Based on them, the effective masses of photon and scalar electron are given. Although we only worked on two toy models, the methods and some of the results can be used to study medium effects in more realistic systems,such as nuclear matter (Hadronic Dynamic Models), electromagnetic plasma (hot QED) and QGP (hot QCD) .