TOPICS ON FIRST-ORDER TRANSITIONS

I review a few issues on first order transitions. The motivation arise s from unexpected peculiarities encountered in numerical simulations o f rather common classical spin systems, and-relative to the finite siz e behaviour of thermodynamical quantities such as the specific heat or higher order energy cumulants. The q-states 2-d Potts model is discus sed in some details, in order to state the problems met as well as to propose explanations and to remedy to their consequences in numerical simulation analysis. Emphasis is put on the relationship between the f inite size behaviour of the partition function and that of the interna l energy distributions.