Toward Understanding the Lattice QCD Results from the Strong Coupling Analysis

This is a review of strong coupling approaches to grasp the nature of thephase transition in finite temperature and density QCD. We commence withclassics of the center symmetry and the Polyakov loop in pure gauge theories.The effective action derived in the strong coupling limit gives qualitativelyplausible behavior for the deconfinement transition at finite temperature. Wecan apply the strong coupling analysis to describe the chiral phase transitionwith the help of large dimensional expansion. In order to make this article asself-contained as possible, we elucidate the computational procedure and itsphysical meaning in detail. Also the relation between the Polyakov loopbehavior and the chiral dynamics, the phase structure of two-color QCD, andfuture possibilities to be pursued in the strong coupling analysis arediscussed.Comment: Contributed to Workshop on Finite Density QCD at Nara, Nara, Japan, 10-12 Jul 200