  We study the relaxation processes of the infinitely long-range interaction
model (the Husimi-Temperley model) near the spinodal point. We propose a
unified finite-size scaling function near the spinodal point, including the
metastable region, the spinodal point, and the unstable region. We explicitly
adopt the Glauber dynamics, derive a master equation for the probability
distribution of the total magnetization, and perform the so-called van Kampen
Omega expansion (an expansion in terms of the inverse of the systems size),
which leads to a Fokker-Planck equation. We analyze the scaling properties of
the Fokker-Planck equation and confirm the obtained scaling plot by direct
numerical solution of the original master equation, and by kinetic Monte Carlo
simulation of the stochastic decay process.
