After a rapid increase in temperature across the deconfinement temperature Tdβ, pure gauge theories exhibit unstable long wavelength fluctuations in
the approach to equilibrium. This phenomenon is analogous to spinodal
decomposition observed in condensed matter physics, and also seen in models of
disordered chiral condensate formation. At high temperature, the unstable modes
occur only in the range 0β€kβ€kcβ, where kcβ is on the order
of the Debye screening mass mDβ. Equilibration always occurs via spinodal
decomposition for SU(2)at temperatures T>Tdβ and for SU(3) for Tβ«Tdβ. For SU(3) at temperatures Tβ³Tdβ, nucleation may replace
spinodal decomposition as the dominant equilibration mechanism. Monte Carlo
simulations of SU(2) lattice gauge theory exhibit the predicted phenomena. The
observed value of kcβ is in reasonable agreement with a value predicted from
previous lattice measurements of mDβ.Comment: minor revisions, 16 pages, 6 figures, RevTe