  To understand the phase transition phenomena, information theoretical
approaches can pick up some important properties of the phenomena based on the
probability distribution. In this paper, we show information theoretical
aspects of the 3-dimensional 3-state Potts model with the external field which
is corresponding to the QCD effective model with heavy quarks. The transfer
mutual information which represents the information flow of two spin variables
is numerically estimated based on the Markov-chain Monte-Carlo method. The
transfer mutual information has the peak near the confinement-deconfinement
transition, and it may be used to detect the precursors of the transition.
Since the transfer mutual information still have the peak even if the
Polyakov-loop changes continuously and smoothly, we may pick up some aspects of
the confinement-deconfinement nature from the information flow properties.
Particularly, the transfer mutual information shows the significantly different
behavior below and above the Roberge-Weiss endpoint existed in the pure
imaginary chemical potential region, which may indicate the system change by
the confinement-deconfinement transition.
