Examples of non-ample normal bundles

Norman Goldstein

Displaying similar documents to “Examples of non-ample normal bundles”

Ample vector bundles with sections vanishing along conic fibrations over curves.

Tommaso De Fernex (1998)

Collectanea Mathematica

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Fano bundles of rank 2 on surfaces

Michał Szurek, Jarosław A. Wisniewski (1990)

Compositio Mathematica

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Geometric genera for ample vector bundles with regular sections.

Antonio Lanteri (2000)

Revista Matemática Complutense

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Let X be a smooth complex projective variety of dimension n ≥ 3. A notion of geometric genus p(X,E) for ample vector bundles E of rank r < n on X admitting some regular sections is introduced. The following inequality holds: p(X,E) ≥ h(X). The question of characterizing equality is discussed and the answer is given for E decomposable of corank 2. Some conjectures suggested by the result are formulated.

On the second exterior power of tangent bundles of threefolds

Frédéric Campana, Thomas Peternell (1992)

Compositio Mathematica

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Remarks on Seshadri constants of vector bundles

Christopher Hacon (2000)

Annales de l'institut Fourier

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We give a lower bound for the Seshadri constants of ample vector bundles which depends only on the numerical properties of the Chern classes and on a “stability” condition.

On generation of jets for vector bundles.

Mauro C. Beltrametti, Sandra Di Rocco, Andrew J. Sommese (1999)

Revista Matemática Complutense

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We introduce and study the k-jet ampleness and the k-jet spannedness for a vector bundle, E, on a projective manifold. We obtain different characterizations of projective space in terms of such positivity properties for E. We compare the 1-jet ampleness with different notions of very ampleness in the literature.

Poincaré bundles for projective surfaces

Nicole Mestrano (1985)

Annales de l'institut Fourier

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Let $X$ be a smooth projective surface, $K$ the canonical divisor, $H$ a very ample divisor and $M_{H} (c_{1}, c_{2})$ the moduli space of rank-two vector bundles, $H$ -stable with Chern classes $c_{1}$ and $c_{2}$ . We prove that, if there exists $c_{1}^{'}$ such that $c_{1}$ is numerically equivalent to $2 c_{1}^{'}$ and if $c_{2} - \frac{1}{4} c_{1}^{2}$ is even, greater or equal to $H^{2} + H K + 4$ , then there is no Poincaré bundle on $M_{H} (c_{1}, c_{2}) \times X$ . Conversely, if there exists $c_{1}^{'}$ such that the number $c_{1}^{'} \cdot c_{1}$ is odd or if $\frac{1}{2} c_{1}^{2} - \frac{1}{2} c_{1} \cdot K - c_{2}$ is odd, then there exists a Poincaré bundle on $M_{H} (c_{1}, c_{2}) \times X$ .