Rank-3 stable bundles on rational rundle ruled surfaces.
Rational projectively Cohen-Macaulay surfaces of maximum degree.
In this paper we determine the greatest degree of a rational projectively Cohen-Macaulay (p.C.M.) surface V in PN and we study the surfaces which attain such maximum degree.
Rationality of Moduli spaces of torsion free sheaves over rational surfaces.
Rationally connected foliations on surfaces.
Real equivalence of complex matrix pencils and complex projections of real Segre varieties.
Real singular Del Pezzo surfaces and 3-folds fibred by rational curves, II
Let be a real smooth projective 3-fold fibred by rational curves such that is orientable. J. Kollár proved that a connected component of is essentially either Seifert fibred or a connected sum of lens spaces. Answering three questions of Kollár, we give sharp estimates on the number and the multiplicities of the Seifert fibres (resp. the number and the torsions of the lens spaces) when is a geometrically rational surface. When is Seifert fibred over a base orbifold , our result generalizes...
Recherches analytiques sur la surface du troisième ordre qui est la réciproque de la surface de Steiner
Remarks on numerically positive line bundles on normal surfaces.
Remarks on the Nagata Conjecture
2000 Mathematics Subject Classification: 14C20, 14E25, 14J26.The famous Nagata Conjecture predicts the lowest degree of a plane curve passing with prescribed multiplicities through given points in general position. We explain how this conjecture extends naturally via multiple point Seshadri constants to ample line bundles on arbitrary surfaces. We show that if there exist curves of unpredictable low degree, then they must have equal multiplicities in all but possibly one of the given points. We...