“Finite temperature QCD and effective actions derived from astrong coupling expansion”

Effective Polyakov loop models provide a useful tool for an
investigation of the phase transition in pure Yang-Mills theory. A
systematic derivation of the effective model can be done in a strong
coupling expansion. With a hopping parameter expansion this approach can
be extended to full QCD, even at finite chemical potential. In this talk
I review the status of the recent investigations of these theories.