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We study motivic Chern classes of cones. First we show examples of projective cones of smooth curves such that their various $K$-classes (sheaf theoretic, push-forward and motivic) are all different. Then we show connections between the…

Algebraic Geometry · Mathematics 2020-06-22 László M. Fehér

This is the continuation of the article by the author that proves a broader class of families admitting the theorem of restriction of sections other than Abelian varieties and gives new examples of pseudo-N\'eron models. In this work, we…

Algebraic Geometry · Mathematics 2019-09-18 Santai Qu

The goal of this short note is to point out that every Fano manifold with a nef tangent bundle possesses an almost K{\"a}hler-Einstein metric, in a weak sense. The technique relies on a regularization theorem for closed positive (1,…

Complex Variables · Mathematics 2018-02-07 Jean-Pierre Demailly

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

Algebraic Geometry · Mathematics 2007-05-23 Qi Zhang

The goal of this work is to pursue the study of pseudo-effective line bundles and vector bundles. Our first result is a generalization of the Hard Lefschetz theorem for cohomology with values in a pseudo-effective line bundle. The Lefschetz…

Algebraic Geometry · Mathematics 2007-05-23 Jean-Pierre Demailly , Thomas Peternell , Michael Schneider

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

In this paper, we prove a second main theorem for a holomorphic curve $f$ into $\mathbb P^N (\mathbb C)$ with a family of slowly moving hypersurfaces $D_1,...,D_q$ with respect to $f$ in $m$-subgeneral position, proving an inequality with…

Complex Variables · Mathematics 2025-01-03 Qili Cai , Chin-Jui Yang

The 2-Fano varieties, defined by De Jong and Starr, satisfy some higher dimensional analogous properties of Fano varieties. We propose a definition of (weak) $k$-Fano variety and conjecture the polyhedrality of the cone of pseudoeffective…

Algebraic Geometry · Mathematics 2024-08-02 Giosuè Emanuele Muratore

We give a new proof of the classification due to Peternell-Szurek-Wi\'{s}niewski of nef vector bundles on a projective space with the first Chern class less than three and on a smooth hyperquadric with the first Chern class less than two…

Algebraic Geometry · Mathematics 2016-07-19 Masahiro Ohno

Let $X$ be a smooth projective variety over the complex numbers. One knows by the Cone Theorem that the closed cone of curves of $X$ is rational polyhedral whenever $c_1(X)$ is ample. For varieties $X$ such that $c_1(X)$ is not ample,…

alg-geom · Mathematics 2007-05-23 Thomas Bauer

We give new proofs of some well-known results from Invariant Theorey using the Kempf-Ness theorem.

Algebraic Geometry · Mathematics 2007-05-23 Ivan V. Losev

We show that nef cycle classes on smooth complete spherical varieties are effective, and the products of nef cycle classes are also nef. Let X be a smooth projective spherical variety such that its effective cycle classes of codimension k…

Algebraic Geometry · Mathematics 2013-11-27 Qifeng LI

This article is concerned with Chern class and Chern number inequalities on polarized manifolds and nef vector bundles. For a polarized pair $(M,L)$ with $L$ very ample, our first main result is a family of sharp Chern class inequalities.…

Differential Geometry · Mathematics 2022-05-11 Ping Li , Fangyang Zheng

In this article, we consider the projective bundle $\mathbb{P}_X(E)$ over a smooth complex projective variety $X$, where $E$ is a semistable bundle on $X$ with $c_2(End(E)) =0$. We give a necessary and sufficient condition to get the…

Algebraic Geometry · Mathematics 2021-02-19 Snehajit Misra

We describe nef vector bundles on a projective space with first Chern class three and second Chern class eight over an algebraically closed field of characteristic zero by giving them a minimal resolution in terms of a full strong…

Algebraic Geometry · Mathematics 2017-08-03 Masahiro Ohno

We classify nef vector bundles on a smooth quadric surface with first Chern class $(2,2)$ over an algebraically closed field of characteristic zero.

Algebraic Geometry · Mathematics 2023-11-07 Masahiro Ohno

In this paper and in its sequel [BKLV], we investigate the cone ${\rm Pseff}_n(C_d)$ of pseudoeffective $n$-cycles in the symmetric product $C_d$ of a smooth curve $C$. In the present paper, we study the convex-geometric properties of the…

Algebraic Geometry · Mathematics 2023-01-18 Francesco Bastianelli , Alexis Kouvidakis , Angelo Felice Lopez , Filippo Viviani

In this paper, we develop a theory of pseudo-effective sheaves on normal projective varieties. As an application, by running the minimal model program, we show that projective klt varieties with pseudo-effective tangent sheaf can be…

Algebraic Geometry · Mathematics 2026-05-27 Shin-ichi Matsumura

Let $C$ be a smooth curve of genus $g \geq 1$ and let $C^{(2)}$ be its second symmetric product. In this note we prove that if $C$ is very general, then the blow-up of $C^{(2)}$ at a very general point has non-polyhedral pseudo-effective…

Algebraic Geometry · Mathematics 2022-10-24 Antonio Laface , Luca Ugaglia

In this paper, we intend to revisit Theorem 2 of [3] formulating it in a way that, weakening the hypotheses and, at the same time, highlighting the richer conclusion allowed by the proof, it can potentially be applicable to a broader range…

Functional Analysis · Mathematics 2013-10-30 Biagio Ricceri