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Remarks on the Nagata Conjecture

Strycharz-Szemberg, Beata, Szemberg, Tomasz (2004)

Serdica Mathematical Journal

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...

Résolution de Nash des points doubles rationnels

Gerardo Gonzalez-Sprinberg (1982)

Annales de l'institut Fourier

Nous présentons une méthode qui permet de calculer le transformée de Nash (et sa normalisation) d’une singularité de surface pour laquelle on dispose d’une résolution explicite. Comme exemple nous calculons la résolution des points doubles rationnels obtenue par itération du transformé de Nash normalisé.

Résolution simultanée d'une famille de singularités rationnelles de surface normale

Michel Vaquié (1985)

Annales de l'institut Fourier

Nous étudions une condition d’équisingularité définie pour une famille de singularités de surface normale par l’existence d’une résolution simultanée très faible et par une condition supplémentaire sur les faisceaux pluricanoniques relatifs. Nous donnons dans le cas d’une famille de singularités rationnelles une condition nécessaire et suffisante portant sur les singularités des fibres pour avoir équisingularité.

Rigidity of CR morphisms between compact strongly pseudoconvex CR manifolds

Stephen S.-T. Yau (2011)

Journal of the European Mathematical Society

Let X 1 and X 2 be two compact strongly pseudoconvex CR manifolds of dimension 2 n - 1 5 which bound complex varieties V 1 and V 2 with only isolated normal singularities in N 1 and N 2 respectively. Let S 1 and S 2 be the singular sets of V 1 and V 2 respectively and S 2 is nonempty. If 2 n - N 2 - 1 1 and the cardinality of S 1 is less than 2 times the cardinality of S 2 , then we prove that any non-constant CR morphism from X 1 to X 2 is necessarily a CR biholomorphism. On the other hand, let X be a compact strongly pseudoconvex CR manifold of...

Semi-simple Carrousels and the Monodromy

David B. Massey (2006)

Annales de l’institut Fourier

Let 𝒰 be an open neighborhood of the origin in n + 1 and let f : ( 𝒰 , 0 ) ( , 0 ) be complex analytic. Let z 0 be a generic linear form on n + 1 . If the relative polar curve Γ f , z 0 1 at the origin is irreducible and the intersection number ( Γ f , z 0 1 · V ( f ) ) 0 is prime, then there are severe restrictions on the possible degree n cohomology of the Milnor fiber at the origin. We also obtain some interesting, weaker, results when ( Γ f , z 0 1 · V ( f ) ) 0 is not prime.

Seshadri positive submanifolds of polarized manifolds

Lucian Bădescu, Mauro Beltrametti (2013)

Open Mathematics

Let Y be a submanifold of dimension y of a polarized complex manifold (X, A) of dimension k ≥ 2, with 1 ≤ y ≤ k−1. We define and study two positivity conditions on Y in (X, A), called Seshadri A-bigness and (a stronger one) Seshadri A-ampleness. In this way we get a natural generalization of the theory initiated by Paoletti in [Paoletti R., Seshadri positive curves in a smooth projective 3-fold, Atti Accad. Naz. Lincei Cl. Sci. Fis. Mat. Natur. Rend. Lincei (9) Mat. Appl., 1996, 6(4), 259–274] (which...

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