  Using Monte Carlo methods, I study the thermodynamic properties of Z_2
Abelian lattice gauge theory in flat, homogeneous, isotropic, expanding
spacetimes characterized by the scale factor a(t). The presence of the scale
factor introduces a spacelike domain wall inside the four dimensional spacetime
lattice where the phase transition associated with deconfinement occurs. The
resulting theory appears identical to introducing a time-dependent effective
coupling beta_eff, and could serve as a simple model for the electroweak phase
transition of the early Universe.
