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Let X be a compact K\"ahler manifold such that the anticanonical bundle $-K_X$ is nef. A classical conjecture claims that the Albanese map is submersive. We prove this conjecture if the general fibre is a weak Fano manifold. If X is…

Algebraic Geometry · Mathematics 2017-10-30 Junyan Cao , Andreas Höring

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 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

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

Let $(X, \omega_X)$ be a compact K\"ahler manifold such that the anticanonical bundle $-K_X$ is nef. We prove that the slopes of the Harder-Narasimhan filtration of the tangent bundle with respect to a polarization of the form…

Algebraic Geometry · Mathematics 2014-02-27 Junyan Cao

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

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 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 show, for several fake projective planes with nontrivial automorphism group, that the bicanonical map is an embedding.

Algebraic Geometry · Mathematics 2018-03-28 Fabrizio Catanese , JongHae Keum

Let $(X, \omega)$ be an n-dimensional compact K\"ahler manifold. Let $D=\sum (1-\beta_j) Y_j=\sum (1-\beta_j) [s_j=0]$ a divisor with simple normal crossings with $\beta_j \in ]0,1[$ such that $-(K_X+D)$ is nef. We show that its Albanese…

Complex Variables · Mathematics 2023-01-13 Xiaojun Wu

In continuation of our paper in Math. Ann. 333 we classify smooth complex projective threefolds X with -K_X big and nef but not ample and Picard number 2, whose anticanonical map is small. We assume also that the Mori contraction of X and…

Algebraic Geometry · Mathematics 2007-10-16 Priska Jahnke , Thomas Peternell , Ivo Radloff

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

In this paper, we prove that a compact K\"ahler manifold $X$ with the nef anti-canonical bundle $-K_{X}$ admits a locally trivial fibration $\phi \colon X \to Y$, where the fiber $F$ is a rationally connected manifold and the base $Y$ is a…

Algebraic Geometry · Mathematics 2025-07-01 Shin-ichi Matsumura , Juanyong Wang , Xiaojun Wu , Qimin Zhang

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

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

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

Let $X$ be a compact complex manifold with trivial canonical bundle and satisfying the $\partial\bar{\partial}$-Lemma. We show that the Kuranishi space of $X$ is a smooth universal deformation and that small deformations enjoy the same…

Differential Geometry · Mathematics 2017-11-15 Ben Anthes , Andrea Cattaneo , Sönke Rollenske , Adriano Tomassini

Let $X$ be a smooth complex projective variety with nef $\bigwedge^2 T_X$ and $\dim X \geq 3$. We prove that, up to a finite \'etale cover $\tilde{X} \to X$, the Albanese map $\tilde{X} \to {\rm Alb}(\tilde{X})$ is a locally trivial…

Algebraic Geometry · Mathematics 2021-04-20 Kiwamu Watanabe

We investigate the structure of smooth projective 3-folds X with -K_X nef and K_X^3=0.

Algebraic Geometry · Mathematics 2007-05-23 Thomas Bauer , Thomas Peternell

Given a fibration $f$ between two projective manifolds $X$ and $Y$, we provide a sufficient condition such that the direct images $f_{\ast}(K_{X/Y}\otimes L\otimes\mathscr{I}(f,\|L\|))$ is nef, where $L$ is a holomorphic line bundle with…

Algebraic Geometry · Mathematics 2021-08-10 Jingcao Wu
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