Minimal models of foliated algebraic surfaces
Minimal varieties with trivial canonical classes, I.
Morphisms of projective varieties from the viewpoint of minimal model theory [Book]
Néron models from the rigid analytic viewpoint
Non-Archimedean integrals and stringy Euler numbers of log-terminal pairs
Using non-Archimedian integration over spaces of arcs of algebraic varieties, we define stringy Euler numbers associated with arbitrary Kawamata log-terminal pairs. There is a natural Kawamata log-terminal pair corresponding to an algebraic variety having a regular action of a finite group . In this situation we show that the stringy Euler number of this pair coincides with the physicists’ orbifold Euler number defined by the Dixon-Harvey-Vafa-Witten formula. As an application, we prove a conjecture...
Non-embeddable -convex manifolds
We show that every small resolution of a 3-dimensional terminal hypersurface singularity can occur on a non-embeddable -convex manifold.We give an explicit example of a non-embeddable manifold containing an irreducible exceptional rational curve with normal bundle of type . To this end we study small resolutions of -singularities.
Numerical character of the effectivity of adjoint line bundles
In this note we show that, for any log-canonical pair , is -effective if its Chern class contains an effective -divisor. Then, we derive some direct corollaries.
On a question of Demailly-Peternell-Schneider
We give an affirmative answer to an open question posed by Demailly-Peternell-Schneider in 2001 and recently by Peternell. Let be a surjective morphism from a log canonical pair onto a -Gorenstein variety . If is nef, we show that is pseudo-effective.
On covering and quasi-unsplit families of curves
Given a covering family of effective 1-cycles on a complex projective variety , we find conditions allowing one to construct a geometric quotient , with regular on the whole of , such that every fiber of is an equivalence class for the equivalence relation naturally defined by . Among other results, we show that on a normal and -factorial projective variety with canonical singularities and , every covering and quasi-unsplit family of rational curves generates a geometric extremal...
On log canonical divisors that are log quasi-numerically positive
Let (X Δ) be a four-dimensional log variety that is projective over the field of complex numbers. Assume that (X, Δ) is not Kawamata log terminal (klt) but divisorial log terminal (dlt). First we introduce the notion of “log quasi-numerically positive”, by relaxing that of “numerically positive”. Next we prove that, if the log canonical divisorK X+Δ is log quasi-numerically positive on (X, Δ) then it is semi-ample.
On minimal models of elliptic threefolds.
On numerically effective log canonical divisors.
On regular threefolds with k = 0.
On some numerical properties of Fano varieties
This is the text of a talk given at the XVII Convegno dellUnione Matematica Italiana held at Milano, September 8-13, 2003. I would like to thank Angelo Lopez and Ciro Ciliberto for the kind invitation to the conference. I survey some numerical conjectures and theorems concerning relations between the index, the pseudo-index and the Picard number of a Fano variety. The results I refer to are contained in the paper [3], wrote in collaboration with Bonavero, Debarre and Druel.
On the birational automorphism groups of algebraic varieties
On the iteration of the adjunction process for surfaces of negative Kodaira dimension.
On the Kodaira Dimension of Minimal Threefolds.
On the length of a extremal rational curve.
On the Minimal Models of Complex Manifolds.
On the minimality of hyperplane sections of projective threefolds.