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Schwarzenberger bundles on smooth projective varieties

TL;DR: Schwarzberger bundles on smooth projective varieties were introduced in this article, and the notions of jumping subspaces and jumping pairs of (F 0, O X ) -Steiner bundles were defined.
About: This article is published in Journal of Pure and Applied Algebra.The article was published on 2016-09-01 and is currently open access. It has received 2 citations till now.

Summary (2 min read)

Introduction

  • Steiner vector bundles on projective spaces were first defined by Dolgachev and Kapranov in [DK93] as vector bundles E fitting in an exact sequence of the form 0→ OPn(−1)s → OtPn → E → 0.
  • Next the authors outline the structure of the paper.
  • In Section 4 the authors obtain an upper bound for the dimension of the jumping variety by studying its tangent space at a fixed jumping pair (see Theorem 4.1).
  • Parts of this work were done in UCM-Madrid, IST-Lisbon and UNICAMPCampinas.

1 Steiner bundles on smooth projective varieties

  • In this section the authors recall the definition of Steiner bundles on smooth projective varieties introduced in [MRS09] and they study some of their properties needed in the sequel.
  • Observe that H0(F∨0 ) is globally generated and is the set of conics that passes through three points.
  • This interpretation will play an essential role for studying Schwarzenberger bundles on X. Proposition 1.5.
  • Then the following properties are equivalent: (i) ϕ is injective.
  • This represents a different and challenging problem in the study of vector bundles and in this paper the authors will not deal with it.

2 Generalized Schwarzenberger on smooth projective vari-

  • The authors goal in this section is to generalize Schwarzenberger bundles on the projective space and on the Grassmann variety G(k, n), as defined in [Arr10] and [AM14], respectively, to any smooth projective variety X. We first recall the definition of Schwarzenberger bundles on G(k, n), following [AM14].the authors.the authors.
  • Given any x ∈ X, the composition (F0)x → H0(ψ∗U∨) of the first two maps (on the second factor) is obviously injective.
  • This construction allows us to generalize the notion of a Schwarzenberger bundle to any smooth projective variety.

4 The tangent space of the jumping variety

  • The authors result will allow us to classify in the next section all Steiner bundles such that J̃(E) has maximal dimension.
  • Recall, furthermore, that Q denotes the vector bundle in (1).
  • In [AM14] the authors proved that the tangent space of the jumping variety at a jumping pair can be also described as TΛJ̃(E) = { ψ ∈ (3) Using this description, the authors are able to obtain an upper bound for the dimension of TΛJ̃(E) and hence an upper bound for the dimension of J̃(E).
  • The authors will prove the statement by defining independent elements in Hom ( Λ, T ∗ Λ ) which are also independent modulo TΛJ̃(E).
  • Observe that the linear map ϕ1 also defines an (F0,OX)-Steiner bundle Ẽ. Consider the bundle morphism Oασ(X) g // ##.

5 The classification

  • OX)-Steiner bundles whose jumping variety has maximal dimension.the authors.
  • In particular, the authors prove that they are always Schwarzenberger bundles.
  • The rest of the section will be devoted to its proof.
  • Let E be a reduced (F0,OX)-Steiner bundle on a smooth projective variety X such that the jumping locus J̃(E) has maximal dimension.

In this case f0 = 1, J̃(E) is a rational normal curve and the natural projections are

  • Moreover, J̃(E) has maximal dimension if and only if J̃(Ē) has maximal dimension, according to the respective bounds.
  • Therefore, when σ is surjective and J̃(E) has maximal dimension, all Steiner bundles on X are Schwarzenberger bundles given by the pullback of the corresponding Schwarzenberger bundle on G(f0−1,P(H0(F∨0 ))), classified in [AM14].
  • Therefore, the authors can suppose, from now on, that σ is not surjective.
  • The generic fibers of π1 and π′1, and the further first component projections given by the induction technique, have respectively dimension either 0 or at least f0.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, the existence of monads on the projective space was shown to be irreducible under certain conditions on the cohomology sheaf of a monad.
Abstract: We generalise Floystad'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 $L$ giving a morphism to the projective space whose image is either arithmetically Cohen-Macaulay (ACM), or linearly normal and not contained in a quadric. We give necessary and sufficient conditions on integers $a$, $b$, and $c$ for a monad of type \[ 0\to(L^\vee)^a\to\mathcal{O}_{X}^{\,b}\to L^c\to0 \] to exist. We show that under certain conditions there exists a monad whose cohomology sheaf is simple. We furthermore characterise low-rank vector bundles that are the cohomology sheaf of some monad as above. Finally, we obtain an irreducible family of monads over the projective space and make a description on how the same method could be used on an ACM smooth projective variety $X$. We establish the existence of a coarse moduli space of low-rank vector bundles over an odd-dimensional $X$ and show that in one case this moduli space is irreducible.

5 citations

Journal ArticleDOI
TL;DR: In this paper, the existence of monads on the projective space was shown to be irreducible under certain conditions on the cohomology sheaf of a monad.
Abstract: We generalise Floystad'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 $L$ giving a morphism to the projective space whose image is either arithmetically Cohen-Macaulay (ACM), or linearly normal and not contained in a quadric. We give necessary and sufficient conditions on integers $a$, $b$, and $c$ for a monad of type \[ 0\to(L^\vee)^a\to\mathcal{O}_{X}^{\,b}\to L^c\to0 \] to exist. We show that under certain conditions there exists a monad whose cohomology sheaf is simple. We furthermore characterise low-rank vector bundles that are the cohomology sheaf of some monad as above. Finally, we obtain an irreducible family of monads over the projective space and make a description on how the same method could be used on an ACM smooth projective variety $X$. We establish the existence of a coarse moduli space of low-rank vector bundles over an odd-dimensional $X$ and show that in one case this moduli space is irreducible.

2 citations

References
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TL;DR: In this paper, the authors introduced the definition of Schwarzenberger bundles on a Grassmannian and generalized the concept of jumping pair for a Steiner bundle on a grassmannian.
Abstract: In this work we introduce the definition of Schwarzenberger bundle on a Grassmannian. Recalling the notion of Steiner bundle, we generalize the concept of jumping pair for a Steiner bundle on a Grassmannian. After studying the jumping locus variety and bounding its dimension, we give a complete classification of Steiner bundle with jumping locus of maximal dimension, which all are Schwarzenberger bundles.

6 citations

Journal ArticleDOI
TL;DR: In this article, the authors define the notion of jumping pairs of a Steiner bundle E on a smooth projective variety X and determine a bound for the dimension of its jumping locus.
Abstract: We define Schwarzenberger bundles on any smooth projective variety X. We introduce the notions of jumping pairs of a Steiner bundle E on X and determine a bound for the dimension of its jumping locus. We completely classify Steiner bundles whose set of jumping pairs have maximal dimension, proving that they are all Schwarzenberger bundles.

3 citations

Frequently Asked Questions (1)
Q1. What are the contributions in "Schwarzenberger bundles on smooth projective varieties" ?

The authors define Schwarzenberger bundles on smooth projective varieties and they introduce the notions of jumping subspaces and jumping pairs of ( F0, OX ) -Steiner bundles.