Sheaves on non-reduced curves in a projective surface

Complete subvarieties in moduli spaces of rank 2 stable sheaves on smooth projective curves and surfaces

The aim of this paper is to prove the existence of large complete subvarieties in moduli spaces of rank two stable sheaves with arbitrary c1 and sufficiently large c2, on algebraic surfaces. Then we study the restriction of these sheaves to curves of high degree embedded in the surface. In the final section we gives a relation with the spin strata defined by Pidstrigach and Tyurin.

Instanton sheaves on complex projective spaces

We study a class of torsion-free sheaves on complex projective spaces which generalize the much studied mathematical instanton bundles. Instanton sheaves can be obtained as cohomologies of linear monads and are shown to be semistable if its rank is not too large, while semistable torsion-free sheaves satisfying certain cohomological conditions are instanton. We also study a few examples of modu...

Maximal Degree Subsheaves of Torsion Free Sheaves on Singular Projective Curves

Fix integers r, k, g with r > k > 0 and g ≥ 2. Let X be an integral projective curve with g := pa(X) and E a rank r torsion free sheaf on X which is a flat limit of a family of locally free sheaves on X. Here we prove the existence of a rank k subsheaf A of E such that r(deg(A)) ≥ k(deg(E)) − k(r − k)g. We show that for every g ≥ 9 there is an integral projective curve X,X not Gorenstein, and a...

Moduli Spaces of Twisted Sheaves on a Projective Variety

Let X be a smooth projective variety over C. Let α := {αijk ∈ H(Ui ∩ Uj ∩ Uk,O X)} be a 2-cocycle representing a torsion class [α] ∈ H2(X,O X). An α-twisted sheaf E := {(Ei, φij)} is a collection of sheaves Ei on Ui and isomorphisms φij : Ei|Ui∩Uj → Ej|Ui∩Uj such that φii = idEi , φji = φ ij and φki ◦ φjk ◦ φij = αijk idEi . We assume that there is a locally free α-twisted sheaf, that is, α giv...

Sheaves on Curves and Their Local Terms