We study a Gibbs measure at a certain temperature,
subject to a stochastic evolution (spin-flip for Ising spins, spin diffusion for XY spins), which has an
invariant measure at a different (high or infinite) temperature. We present various results about when the
evolved measure in the transient regime can be written as a Gibbs measure for some effective interaction. The
norm of such an inverse interaction has an interpretation as an inverse temperature.