Cohomological property of vector bundles on biprojective spaces

This paper investigates the cohomological property of vector bundles on biprojective space. We will give a criterion for a vector bundle to be isomorphic to the tensor product of pullbacks of exterior products of differential sheaves.

     

Some extensions of horrocks criterion to vector bundles on Grassmannians and quadrics

Summary In this paper we prove that a vector bundle E on a grassmannian (resp. on a quadric) splits as a direct sum of line bundles if and only if certain cohomology groups involving E and the quotient bundle (resp. the spinor bundle) are zero. When rank E=2 a better criterion is obtained considering only finitely many suitably chosen cohomology groups.This paper has been written while the author was enrolled in the Research Doctorate of the University of Florence. Partially supported by MPI 40% funds.     

Representations of elementary abelian p-groups and bundles on Grassmannians

We initiate the study of representations of elementary abelian p-groups via restrictions to truncated polynomial subalgebras of the group algebra generated by r nilpotent elements, $k[t_1,\dots ,t_r]/(t_1^p,\dots ,t_r^p)$. We introduce new geometric invariants based on the behavior of modules upon restrictions to such subalgebras. We also introduce modules of constant radical and socle type generalizing modules of constant Jordan type and provide several general constructions of modules with these properties. We show that modules of constant radical and socle type lead to families of algebraic vector bundles on Grassmannians and illustrate our theory with numerous examples.     

Fuzzy complex Grassmannians and quantization of line bundles

We construct by purely representation-theoretic methods fuzzy versions of an arbitrary complex Grassmannian M=Gr _n (ℂ ^n+m ), i.e., a sequence of matrix algebras tending SU(n+m)-equivariantly to the algebra of smooth functions on M. We also show that this approximation can be interpreted in terms of the Berezin-Toeplitz quantization of M. Furthermore, we use branching rules to prove that the quantization of every complex line bundle over M is given by a SU(n+m)-equivariant truncation of the space of its L ²-sections.     

Cohomological barriers to the extension of holomorphic line bundles

For holomorphic line bundles with L² -bounded curvature we prove an theorem on extension across an analytic subset and construct a counterexample to extension across a smooth noncomplex submanifold of codimension 2.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 34, 1991, pp. 4–8.     

Vector bundles over Grassmannians and the skew-symmetric curvature operator

A pseudo-Riemannian manifold is said to be spacelike Jordan IP if the Jordan normal form of the skew-symmetric curvature operator depends upon the point of the manifold, but not upon the particular spacelike 2-plane in the tangent bundle at that point. We use methods of algebraic topology to classify connected spacelike Jordan IP pseudo-Riemannian manifolds of signature (p,q), where q?11, and where the set {q,…,q+p} does not contain a power of 2.     

Uniform vector bundles on quadrics

Summary In this paper we prove that a rankr uniform vector bundle on a nonsingular quadricQ with dimQ≥2r+2 is a direct sum of line bundles. We study also rank 2 uniform vector bundles onP ₁×P₁. We prove that they are not all homogeneous and that any rank 2 homogeneous vector bundles onP ₁×P₁ is decomposable.

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Riassunto In questo lavoro si dimostra che un fibrato uniforme di rangor su una quadrica non singolareQ con dimQ≥2r+2 è somma diretta di fibrati in rette. Si studiano poi i fibrati uniformi di rango 2 suP ₁×P₁. Si dimostra che non sono tutti omogenei e che ogni fibrato omogeneo di rango 2 suP ₁×P₁ è decomponibile.

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The author is member of G.N.S.A.G.A. of C.N.R.     

ACM vector bundles on scrolls

Here we show that certain low rank ACM vector bundles on scrolls over smooth curves are iterated extensions of line bundles. Partially supported by MIUR and GNSAGA of INDAM (Italy)     

On jumping lines of vector bundles on $$\mathbb {P}^n$$

We give bounds on the rank of non uniform vector bundles on \(\mathbb {P}^n\) with a finite number of jumping lines.     

Raynaud vector bundles

We construct vector bundles on a smooth projective curve X having the property that for all sheaves E of slope μ and rank rk on X we have an equivalence: E is a semistable vector bundle . As a byproduct of our construction we obtain effective bounds on r such that the linear system |R·Θ| has base points on U _X (r, r(g − 1)).      

Exceptional collections for Grassmannians of isotropic lines

We construct a full exceptional collection of vector bundlesin the derived categories of coherent sheaves on the Grassmannianof isotropic two-dimensional subspaces in a symplectic vectorspace of dimension 2n and in an orthogonal vector space of dimension2n + 1 for all n.