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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

In this article we prove new results on projective normality and normal presentation of adjunction bundle associated to an ample and globally generated line bundle on higher dimensional smooth projective varieties with nef canonical bundle.…

Algebraic Geometry · Mathematics 2019-09-10 Jayan Mukherjee , Debaditya Raychaudhury

We prove that the Albanese map of a smooth projective threefold, whose anticanonical bundle is nef, is a surjective submersion. We also investigate morphisms of threefolds to curves and surfaces whose relative anticanonical bundle are nef.

Algebraic Geometry · Mathematics 2007-05-23 Thomas Peternell , Fernando Serrano

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

Suppose that $X$ is a projective manifold whose tangent bundle $T_X$ contains a locally free strictly nef subsheaf. We prove that $X$ is isomorphic to a projective bundle over a hyperbolic manifold. Moreover, if the fundamental group…

Algebraic Geometry · Mathematics 2020-04-21 Jie Liu , Wenhao Ou , Xiaokui Yang

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 prove a structure theorem for projective varieties with nef anticanonical divisors.

Algebraic Geometry · Mathematics 2007-05-23 Qi Zhang

In this paper, we prove that a non-projective compact K\"ahler three-fold with nef anti-canonical bundle is, up to a finite \'etale cover, one of the following: a manifold with vanishing first Chern class; the product of a K3 surface and…

Algebraic Geometry · Mathematics 2025-01-09 Shin-ichi Matsumura , Xiaojun Wu

In this paper we prove that the anti-canonical bundle of a holomorphic foliation $\mathcal{F}$ on a complex projective manifold cannot be nef and big if either $\mathcal{F}$ is regular, or $\mathcal{F}$ has a compact leaf. Then we address…

Algebraic Geometry · Mathematics 2015-07-23 Stéphane Druel

The paper consists of three parts. In the first of them different kinds stability are discussed. In particular, the stability concept with respect to nef divisor is introduced. A structure of rigid and superrigid vector bundles on smooth…

alg-geom · Mathematics 2008-02-03 Sergej A. Kuleshov

Let $X$ be a smooth projective variety with a nef anticanonical divisor over an algebraically closed field of characteristic $p>0$. In this paper, we establish a precise structure of $X$ under the condition that $a_X: X \to {\rm Alb}(X)$ is…

Algebraic Geometry · Mathematics 2025-10-21 Tongji Gao , Zhan Li , Lei Zhang

In this note, we describe the structure of regular foliations with semi-positive anti-canonical bundle on smooth projective varieties.

Algebraic Geometry · Mathematics 2018-10-17 Stéphane Druel

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

In this article we study the structure of klt projective varieties with nef anticanonical divisor (and more generally, varieties of semi-Fano type), especially the canonical fibrations associated to them. We show that: 1. the Albanese map…

Algebraic Geometry · Mathematics 2020-09-15 Juanyong Wang

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 study the structure of the Albanese map for K\"ahler manifolds with nef anticanonical bundle. First, we give a result for fourfolds whose Albanse torus is an elliptic curve. In the general case of any dimension, we look at two cases: The…

Algebraic Geometry · Mathematics 2024-02-22 Philipp Naumann , Xiaojun Wu

Projective spaces for finite-dimensional vector spaces over general fields are considered. The geometry of these spaces and the theory of line bundles over these spaces is presented. Particularly, the space of global regular sections of…

Algebraic Geometry · Mathematics 2023-09-21 Andrew D. Lewis

In this paper, we study smooth complex projective varieties $X$ such that some exterior power $\bigwedge^r T_X$ of the tangent bundle is strictly nef. We prove that such varieties are rationally connected. We also classify the following two…

Algebraic Geometry · Mathematics 2018-11-29 Duo Li , Wenhao Ou , Xiaokui Yang

We start the classification of smooth projective threefolds X whose anticanonical bundles -K_X are big and nef but not ample. In this paper we treat the case b_2(X) = 2 and the morphism associated with the base point free linear system…

Algebraic Geometry · Mathematics 2007-05-23 Priska Jahnke , Thomas Peternell , Ivo Radloff

Let X be a simply connected projective manifold with nef anticanonical bundle. We prove that X is a product of a rationally connected manifold and a manifold with trivial canonical bundle. As an application we describe the MRC fibration of…

Algebraic Geometry · Mathematics 2017-06-28 Junyan Cao , Andreas Höring
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