  The density distributions and Soret coefficient in a nonequilibrium colloidal
system with nonuniform temperature are studied by the overdamped Langevin
equation for Brownian motion in an inhomogeneous strong friction medium. Based
on the relation between the temperature gradient, the interaction potential and
the q-parameter in nonextensive statistics, We show that the colloidal particle
density can be a function of the temperature and anomalously follows the noted
alpha-distribution, or equivalently it can also be a function of the potential
energy and follows Tsallis distribution. With the q-parameter we can establish
a new formula of the Soret coefficient and thus, bridge the gap between the
ideally theoretical Soret coefficient and available experiments.
