Effects of chiral restoration on the behaviour of the Polyakov loop at strong coupling

We discuss the relation between the Polyakov loop and the chiral order parameter at finite temperature. For that purpose we analyse an effective model proposed by Gocksch and Ogilvie, which is constructed by the double expansion of strong coupling and large dimensionality. We make improvements in dealing with the model and then obtain plausible results for the behaviours of both the Polyakov loop and the chiral scalar condensate. The pseudo-critical temperature read from the Polyakov loop turns out to coincide exactly with that read from the chiral scalar condensate. Within the model study based on the strong coupling expansion, the coincidence of the pseudo-critical temperatures results from the fact that the jump of the Polyakov loop in the presence of dynamical quarks should signify the chiral phase transition rather than the deconfinement transition.