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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 develop a theory of conically smooth stratified spaces and their smooth moduli, including a notion of classifying maps for tangential structures. We characterize continuous space-valued sheaves on these conically smooth stratified spaces…

Algebraic Topology · Mathematics 2017-02-10 David Ayala , John Francis , Hiro Lee Tanaka

We prove some general results on syzygies of smooth projective varieties with numerically trivial canonical line bundle. This allows to confirm several cases of Mukai's syzygies conjecture for finite quotients of abelian varieties in any…

Algebraic Geometry · Mathematics 2025-09-22 Federico Caucci

In this paper we prove a generalization of a theorem of Schneider, which gives a criterion for a projective surface over the complex numbers to have an ample cotangent bundle. After reviewing different notions of positivity, we introduce a…

Algebraic Geometry · Mathematics 2010-02-04 Kelly Jabbusch

For a smooth curve of genus $g$ embedded by a line bundle of degree at least $2g+3$ we show that the ideal sheaf of the secant variety is 5-regular. This bound is sharp with respect to both the degree of the embedding and the bound on the…

Algebraic Geometry · Mathematics 2007-10-23 Peter Vermeire

We study the positivity of exterior powers of the tangent sheaf on toric varieties in order to generalize results by Campana and Peternell about 3-folds with nef second exterior power of the tangent bundle. Using the theory of equivariant…

Algebraic Geometry · Mathematics 2018-11-08 David Schmitz

The goal of this work is to prove an embedding theorem for compact almost complex manifolds into complex algebraic varieties. It is shown that every almost complex structure can be realized by the transverse structure to an algebraic…

Complex Variables · Mathematics 2016-07-18 Jean-Pierre Demailly , Hervé Gaussier

We generalise Fl\o{}ystad's theorem on the existence of monads on the projective space to a larger set of projective varieties. We consider a variety $X$, a line bundle $L$ on $X$, and a base-point-free linear system of sections of $L$…

Algebraic Geometry · Mathematics 2018-06-18 Simone Marchesi , Pedro Macias Marques , Helena Soares

We prove that the tangent bundle of a generic space of planar n-gons with specified side lengths, identified under isometry, plus a trivial line bundle is isomorphic to (n-2) times a canonical line bundle. We then discuss consequences for…

Algebraic Topology · Mathematics 2018-05-09 Donald M. Davis

Let $K$ be the function field of a smooth curve over an algebraically closed field $k$. Let $X$ be a scheme, which is smooth and projective over $K$. Suppose that the cotangent bundle $\Omega_{X/K}$ is ample. Let $R:={\rm Zar}(X)(K)\cap X)$…

Algebraic Geometry · Mathematics 2017-06-27 Henri Gillet , Damian Rössler

Classification theory and the study of projective varieties which are covered by rational curves of minimal degrees naturally leads to the study of families of singular rational curves. Since families of arbitrarily singular curves are hard…

Algebraic Geometry · Mathematics 2007-05-23 Stefan Kebekus

We totally classify the projective toric varieties whose canonical divisors are divisible by their dimensions. In Appendix, we show that Reid's toric Mori theory implies Mabuchi's characterization of the projective space for toric…

Algebraic Geometry · Mathematics 2007-05-23 Osamu Fujino

We prove that the multiplication of sections of globally generated line bundles on a model wonderful variety M of simply connected type is always surjective. This follows by a general argument which works for every wonderful variety and…

Algebraic Geometry · Mathematics 2018-06-26 Paolo Bravi , Jacopo Gandini , Andrea Maffei

Let $X$ be a projective nonsingular toric 3-fold with a surjective torus equivariant morphism onto the projective line. Then we prove that an ample line bundle on $X$ is always normally generated.

Algebraic Geometry · Mathematics 2023-09-21 Shoetsu Ogata

Let X be a smooth, complete, toric variety. We study those curves C in X that are contractible, in the sense that there exists an equivariant morphism with connected fibers, with source X, that contracts exactly the irreducible curves that…

Algebraic Geometry · Mathematics 2007-05-23 Cinzia Casagrande

We study the relations between the triviality of the tangent bundle $TM$ and the generalized tangent bundle $\mathbb{T}M = TM\oplus T^*M$ of a manifold. We show that the generalized tangent bundle of a paralellizable manifold is trivial. We…

Differential Geometry · Mathematics 2026-05-18 Fernando Etayo , Pablo Gómez-Nicolás , Rafael Santamaría

I prove a crystalline characterization of abelian varieties in characteristic $p>0$ amongst the class of varieties with trivial tangent bundle. I show using my characterization that a smooth, projective, ordinary variety with trivial…

Algebraic Geometry · Mathematics 2020-12-07 Kirti Joshi

We confirm Beauville's conjecture that claims that if the p-th exterior power of the tangent bundle of a smooth projective variety contains the p-th power of an ample line bundle, then the variety is either the projective space or the…

Algebraic Geometry · Mathematics 2009-11-13 Carolina Araujo , Stéphane Druel , Sándor J. Kovács

We show that the vector bundle associated to a smooth projective connected finite covering of a simple complex abelian variety is ample (under a simple necessary condition). This result is obtained by showing that this bundle is M-regular…

Algebraic Geometry · Mathematics 2007-05-23 Olivier Debarre

We show that smooth projective horospherical varieties with nef tangent bundles are rational homogeneous spaces.

Algebraic Geometry · Mathematics 2015-12-16 Qifeng Li