Abstract
We propose a framework to describe nonequilibrium dynamics with respect to a set of macroscopic variables by assuming that microscopic states that have the same corresponding macroscopic variables appear with equal-probability, i.e., the nonequilibrium state is treated as an extended microcanonical ensemble. The method is numerically examined by the relaxation dynamics of the two dimensional Potts model with temperature fixed, and it is found that the two-variable (energy and magnetization) description gives much more quantitatively accurate prediction than the one-variable (energy) description, which is sufficient for equilibrium states. This means that the transient states are difficult to be approximated by the equilibrium state fixing temperature, but possible by the one fixing temperature and magnetic field.
