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We study the geometry of projective manifolds whose tangent bundles are nef on sufficiently general curves (i.e. the tangent bundle is generically nef) and show that manifolds whose anticanonical bundles are semi-ample have this property.…

Algebraic Geometry · Mathematics 2008-07-08 Thomas Peternell

We show that the tangent bundle of a projective manifold with nef anticanonical class is generically nef. That is, its restriction to a curve cut out by general sufficiently ample divisors is a nef vector bundle. This confirms a conjecture…

Algebraic Geometry · Mathematics 2021-08-03 Wenhao Ou

We prove that under a finite surjective map of irreducible smooth complex projective curves, the pullback and direct image of a parabolic ample (respectively, parabolic nef) vector bundle is again parabolic ample (respectively, parabolic…

Algebraic Geometry · Mathematics 2026-01-27 Ashima Bansal , Indranil Biswas

Given a covering f: X \to Y of projective manifolds, we consider the vector bundle E on Y given as the dual of f_*(\O_X) / \O_Y. This vector bundles often has positivity properties, e.g. E is ample when Y is projective space by a theorem of…

Algebraic Geometry · Mathematics 2007-05-23 Thomas Peternell , Andrew J. Sommese

In this paper, we show that if the tangent bundle of a smooth projective variety is strictly nef, then it is isomorphic to a projective space; if a projective variety $X^n$ $(n>4)$ has strictly nef $\Lambda^2 TX$, then it is isomorphic to…

Algebraic Geometry · Mathematics 2018-01-31 Duo Li , Xiaokui Yang

We show that an equivariant vector bundle on a complete toric variety is nef or ample if and only if its restriction to every invariant curve is nef or ample, respectively. Furthermore, we show that nef toric vector bundles have a…

Algebraic Geometry · Mathematics 2010-07-09 Milena Hering , Mircea Mustata , Sam Payne

We show that tensor products of semiample vector bundles are semiample. For k-ampleness in the sens of Sommese, we show that over compact complex manifolds tensor products of semiample and k-ample vector bundles are k-ample, and the sum of…

Algebraic Geometry · Mathematics 2016-07-26 F. Laytimi , W. Nahm

In this note, we give a brief exposition on the differences and similarities between strictly nef and ample vector bundles, with particular focus on the circle of problems surrounding the geometry of projective manifolds with strictly nef…

Algebraic Geometry · Mathematics 2020-09-03 Jie Liu , Wenhao Ou , Xiaokui Yang

We give the first examples of nef line bundles on smooth projective varieties over finite fields which are not semi-ample. More concretely, we find smooth curves on smooth projective surfaces over finite fields such that the normal bundle…

Algebraic Geometry · Mathematics 2007-12-14 Burt Totaro

In this paper, we study when positivity conditions of vector bundles are preserved by extension. We prove that an extension of a big (resp. pseudo-effective) line bundle by an ample (resp. a nef) vector bundle is big (resp.…

Algebraic Geometry · Mathematics 2023-12-18 Sho Ejiri , Osamu Fujino , Masataka Iwai

In this paper, we study the structure of projective space bundles whose relative anti-canonical line bundle is nef. As an application, we get a characterization of abelian varieties up to finite etale covering.

Algebraic Geometry · Mathematics 2011-10-10 Kazunori Yasutake

We study ample stable vector bundles on minimal rational surfaces. We give a complete classification of those moduli spaces for which the general stable bundle is both ample and globally generated. We also prove that if $V$ is any stable…

Algebraic Geometry · Mathematics 2021-07-22 Jack Huizenga , John Kopper

The cotangent bundle of a non-uniruled projective manifold is generically nef, due to a theorem of Miyaoka. We show that the cotangent bundle is actually generically ample, if the manifold is of general type and study in detail the case of…

Algebraic Geometry · Mathematics 2011-06-22 Thomas Peternell

In this note, we discuss the concept of pseudoeffective vector bundle and also introduce pseudoeffective torsion-free sheaves over compact K\"ahler manifolds. We show that a pseudoeffective reflexive sheaf over a compact K\"ahler manifold…

Algebraic Geometry · Mathematics 2022-04-29 Xiaojun Wu

In the first part of this note, we discuss the compact K\"ahler manifold with a strongly pseudo-effective tangent bundle. In the second part, we give new proof of the fact that the only projective manifolds with the big tangent bundle are…

Differential Geometry · Mathematics 2024-01-02 Xiaojun Wu

Up to finite \'etale cover, any smooth complex projective variety $X$ with nef anti-canonical bundle is a holomorphic fibre bundle over a $K$-trivial variety with locally constant transition functions. We show that this result is optimal by…

Algebraic Geometry · Mathematics 2025-03-26 Niklas Müller

We classify nef vector bundles on a smooth hyperquadric of dimension three with first Chern class two over an algebraically closed field of characteristic zero. In particular, we see that they are globally generated.

Algebraic Geometry · Mathematics 2025-06-25 Masahiro Ohno

This is a survey article on recent results on vector bundles on symmetric product of non-singular projective curves.

Algebraic Geometry · Mathematics 2017-02-20 D. S. Nagaraj

In this paper, we prove that given a flat generically smooth morphism between smooth projective varieties with $F$-pure closed fibers, if the source space is Fano, weak Fano or a variety with the nef anti-canonical divisor, then so is the…

Algebraic Geometry · Mathematics 2019-12-11 Sho Ejiri

Let X be a smooth projective variety defined over an algebraically closed field k. Nori constructed a category of vector bundles on X, called essentially finite vector bundles, which is reminiscent of the category of representations of the…

Algebraic Geometry · Mathematics 2009-12-21 Indranil Biswas , Joao Pedro P. dos Santos
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