Maximal degree subsheaves of torsion free sheaves on singular projective curves

Authors
Citation
E. Ballico, Maximal degree subsheaves of torsion free sheaves on singular projective curves, T AM MATH S, 353(9), 2001, pp. 3617-3627
Citations number
17
Categorie Soggetti
Mathematics
Journal title
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY
ISSN journal
00029947 → ACNP
Volume
353
Issue
9
Year of publication
2001
Pages
3617 - 3627
Database
ISI
SICI code
0002-9947(2001)353:9<3617:MDSOTF>2.0.ZU;2-I
Abstract
Fix integers r, k, g with r > k > 0 and g greater than or equal to 2. Let X be an integral projective curve with g := p(a)(X) and E a rank r torsion f ree 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)) greater than or equal to k(deg(E)) - k(r - k)g. We show that for every g greater than or equal to 9 there is an integral projective curve X, X no t Gorenstein, and a rank 2 torsion free sheaf E on X with no rank 1 subshea f A with 2(deg(A)) greater than or equal to deg(E) - g. We show the existen ce of torsion free sheaves on non-Gorenstein projective curves with other p athological properties.