Mathematics – Algebraic Geometry
Scientific paper
2008-03-07
Canad. J. Math. 62 (2010), 1131-1154
Mathematics
Algebraic Geometry
19 pages
Scientific paper
Let \sF be a coherent rank 2 sheaf on a scheme Y \subset \proj{n} of dimension at least two. In this paper we study the relationship between the functor which deforms a pair (\sF,\sigma), \sigma \in H^0(\sF), and the functor which deforms the corresponding pair (X,\xi) given as in the Serre correspondence. We prove that the scheme structure of e.g. the moduli scheme M_Y(P) of stable sheaves on a threefold Y at (\sF), and the scheme structure at (X) of the Hilbert scheme of curves on Y are closely related. Using this relationship we get criteria for the dimension and smoothness of M_Y(P) at (\sF), without assuming Ext^2(\sF,\sF) = 0. For reflexive sheaves on Y = \proj{3} whose deficiency module M = H_{*}^1(\sF) satisfies Ext^2(M,M) = 0 in degree zero (e.g. of diameter at most 2), we get necessary and sufficient conditions of unobstructedness which coincide in the diameter one case. The conditions are further equivalent to the vanishing of certain graded Betti numbers of the free graded minimal resolution of H_{*}^0(\sF). It follows that every irreducible component of M_{\proj{3}}(P) containing a reflexive sheaf of diameter one is reduced (generically smooth). We also determine a good lower bound for the dimension of any component of M_{\proj{3}}(P) which contains a reflexive stable sheaf with "small" deficiency module M.
No associations
LandOfFree
Moduli spaces of reflexive sheaves of rank 2 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Moduli spaces of reflexive sheaves of rank 2, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moduli spaces of reflexive sheaves of rank 2 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-252942