... "What do you call work?" "Why ain't that work?" Tom resumed his
whitewashing, and answered carelessly: "Well. lI1a), he it is, and maybe
it aill't. All I know, is, it suits Tom Sawvc/: " "Oil CO/lll!, IIOW,
Will do not mean to let 011 that you like it?" The brush continued to
move. "Likc it? Well, I do not see wlzy I oughtn't to like it. Does a
hoy get a chance to whitewash a fence every day?" That put the thing ill
a Ilew light. Ben stopped nibhling the apple .... (From Mark Twain's
Adventures of Tom Sawyer, Chapter II.) Mathematics can put quantitative
phenomena in a new light; in turn applications may provide a vivid
support for mathematical concepts. This volume illustrates some aspects
of the mathematical treatment of phase transitions, namely, the
classical Stefan problem and its generalizations. The in- tended reader
is a researcher in application-oriented mathematics. An effort has been
made to make a part of the book accessible to beginners, as well as
physicists and engineers with a mathematical background. Some room has
also been devoted to illustrate analytical tools. This volume deals with
research I initiated when I was affiliated with the Istituto di Analisi
Numerica del C.N.R. in Pavia, and then continued at the Dipartimento di
Matematica dell'Universita di Trento. It was typeset by the author in
plain TEX.