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We study global primary decompositions in the category of sheaves on a scheme which are equivariant under the action of an algebraic group. We show that equivariant primary decompositions exist if the group is connected. As main application…

Algebraic Geometry · Mathematics 2012-01-30 Markus Perling , Guenther Trautmann

Let A be an ample line bundle on a projective toric variety X of dimension n. We show that if l>=n-1+p, then A^l satisfies the property N_p. Applying similar methods, we obtain a combinatorial theorem: For a given lattice polytope P we give…

Algebraic Geometry · Mathematics 2007-05-23 Milena Hering

A torsion free sheaf on a hyperk\"ahler variety $X$ is modular if the discriminant satisfies a certain condition, for example if it is a multiple of $c_2(X)$ the sheaf is modular. The definition is taylor made for torsion-free sheaves on a…

Algebraic Geometry · Mathematics 2021-04-28 Kieran G. O'Grady

We study the proalgebraic space which is the inverse limit of all finite branched covers over a normal toric variety with branching set the invariant divisor under the algebraic torus action. These are completions (compactifications) of the…

Algebraic Geometry · Mathematics 2021-11-16 Juan M. Burgos , Alberto Verjovsky

In this note, (rational) Betti numbers of homotopy colimits for toric diagrams and their classifying spaces are described in terms of sheaf cohomology over CW posets. We prove for any $T$-diagram $D$ over any CW poset that…

Algebraic Topology · Mathematics 2026-04-30 Grigory Solomadin

We show that every action of a smooth algebraic group on a variety admits a normal projective model. Along the way, we present new proofs of some basic results on algebraic transformation groups, including Weil's regularization theorem.

Algebraic Geometry · Mathematics 2022-08-15 Michel Brion

The automorphism group of a projective bundle P(E) over a simplicial toric variety is described when the bundle E is a direct sum of line bundles. Applications to study of moduli of complete intersections on toric varieties, including…

Algebraic Geometry · Mathematics 2007-05-23 Amassa Fauntleroy

For a smooth toric variety X over a field of positive characteristic, a T-equivariant \'{e}tale cover Y \rightarrow T^*X^{(1)} trivializing the sheaf of crystalline differential operators on X is constructed. This trivialization is used to…

Algebraic Geometry · Mathematics 2011-02-22 Theodore J. Stadnik

Toric varieties are a special class of rational varieties defined by equations of the form {\it monomial = monomial}. For a good brief survey of the history and role of toric varieties see [10]. Any toric variety $X$ contains a cover by…

alg-geom · Mathematics 2008-02-03 Frank DeMeyer , Tim Ford , Rick Miranda

We show that if X is a smooth rationally connected threefold and C is a smooth projective curve then C can be embedded in X. Furthermore, a version of this property characterises rationally connected varieties of dimension at least 3. We…

Algebraic Geometry · Mathematics 2010-02-05 G. K. Sankaran

We study two classes of morphisms in infinite type: tamely presented morphisms and morphisms with coherent pullback. These are generalizations of finitely presented morphisms and morphisms of finite Tor-dimension, respectively. The class of…

Algebraic Geometry · Mathematics 2024-01-11 Sabin Cautis , Harold Williams

We develop a theory of general sheaves over weighted projective lines. We define and study a canonical decomposition, analogous to Kac's canonical decomposition for representations of quivers, study subsheaves of a general sheaf, general…

Algebraic Geometry · Mathematics 2007-09-24 William Crawley-Boevey

In this article, we investigate Hecke modifications of vector bundles on a smooth projective curve $X$ defined over an arbitrary field. We obtain structural results that allow us to reduce the classification problem of Hecke modifications…

Algebraic Geometry · Mathematics 2025-06-03 Roberto Alvarenga , Leonardo Moço

We study holomorphic foliations of aribitrary codimension in smooth complete toric varieties. We show that split foliations are stable if some good behaviour of their singular set is provided. As an application of these results, we exhibit…

Algebraic Geometry · Mathematics 2022-01-25 Sebastián Velazquez

Let $X$ be a connected compact complex manifold admitting a finite surjective map $A \to X$ from a complex torus $A.$ We prove that up to finite \'etale cover, $X$ is a product of projective spaces and a torus.

Algebraic Geometry · Mathematics 2008-02-25 Jean-Pierre Demailly , Jun-Muk Hwang , Thomas Peternell

Let $F$ be a torsionfree semistable coherent sheaf on a polarized normal projective variety. We prove that $F$ has a unique maximal locally free subsheaf $V$ such that $F/V$ is torsionfree and $V$ admits a filtration of subbundles for which…

Algebraic Geometry · Mathematics 2021-06-08 Indranil Biswas , A. J. Parameswaran

We give a proof of the $p$-adic weight monodromy conjecture for scheme-theoretic complete intersections in projective smooth toric varieties. The strategy is based on Scholze's proof in the $\ell$-adic setting, which we adapt using…

Algebraic Geometry · Mathematics 2025-06-11 Federico Binda , Hiroki Kato , Alberto Vezzani

In this paper, we establish a structure theorem for a smooth projective variety $X$ with semi-positive holomorphic sectional curvature. Our structure theorem contains the solution for Yau's conjecture and it can be regarded as a natural…

Differential Geometry · Mathematics 2018-11-13 Shin-ichi Matsumura

We examine Li's double determinantal varieties in the special case that they are toric. We recover from the general double determinantal varieties case, via a more elementary argument, that they are irreducible and show that toric double…

Commutative Algebra · Mathematics 2020-06-09 Alexander Blose , Patricia Klein , Owen McGrath , Jackson Morris

In this paper, we establish an innovative framework in logarithmic Hodge theory for toroidal varieties, introducing weighted toroidal structures and developing a systematic obstruction theory for Hodge classes. Building upon recent advances…

Algebraic Geometry · Mathematics 2025-09-30 Jiaming Luo