Fluctuations of order parameter in an $SU(N_c)$ effective model

We investigate features of the deconfinement phase transition in an $SU(N_c)$ gauge theory as revealed by fluctuations of the order parameter. The tool of choice is an effective model built from one-loop expressions of the field determinants of gluon and ghost, in the presence of a Polyakov loop background field. We show that the curvature masses associated with the Cartan angles, which serve as a proxy to study the $A_0$-gluon screening mass, show a characteristic dip in the vicinity of the transition temperature. The strength of the observables, which reflects a competition between the confining and the deconfining forces, is sensitive to assumptions of dynamics, thus provides an interesting link between the $Z(N_c)$ vacuum structure and the properties of gluon and ghost propagators.