Sunto: Lo scopo del programma dei modelli minimali (Minimal Model Program)
e' di generalizzare la classificazione delle superficie proiettive
complesse, gia' nota nella prima meta' del 900, a varieta' di dimensione
superiore. Dopo una breve introduzione storica, discuteremo alcuni
risultati recenti e aspetti nuovi
di questo programma.
ABSTRACT: The main result which I want to present is, grosso-modo, the
following: Let X be a smooth variety, Y a (locally) Cohen-Macaulay
scheme structure on X, ie such that Y_{red}=X. Then there are three
canonical filtrations of Y with "less and less nilpotent" closed
subschemes, such that the graded objects associated to the sequence
of the sheaves of ideals are: B(Y)=a graded O_X-algebra, A(Y)= a
graded B(Y)-algebra, M(Y) a graded A(Y)-module. One can
characterize those Y which are Gorenstein by properties of these
graded objects.