RAPID TEMPERATURE-CHANGES NEAR A CRITICAL-POINT

The appearance or disappearance of a wide range of critical fluctuatio ns following a sudden temperature change is investigated theoretically . On large length scales a temperature step away from criticality gene rates a nonequilibrium free field. For a step towards the critical poi nt, the approach to equilibrium is characterized by an equilibration l ength lambda(eq) that depends on time t. A power law for lambda(eq)(t) similar to t(p) with p approximate to 0.32 is derived from scaling arg uments. The theory predicts a power law approach of the temperature to the new equilibrium with an exponent depending on whether the tempera ture is initially increased or decreased.