THERMAL FLUCTUATIONS AT 2ND-ORDER PHASE-TRANSITIONS

We construct a new coarse-grained effective potential which enables us to estimate the probabilities of thermal fluctuations above an arbitr ary threshold at different length scales. This potential is convex, an d converges to the usual effective potential in the limit that the coa rse-graining volume becomes infinite. We use it to gain new insight in to the meaning of the Ginzburg temperature, and briefly consider the r ole of defects in supplying large ''subcritical'' fluctuations at the phase transition.