2003/02/19 by Holger Brenner
Mathematics · #math.AG #math.AC #msc:13A35 #msc:14H60
published as Trans. Amer. Math. Soc. 356, 1 (2004), 371 - 392.
arxiv created 2003/02/19 · arxiv updated 2009/11/30
We study different notions of slope of a vector bundle over a smooth projective curve with respect to ampleness and affineness in order to apply this to tight closure problems. This method gives new degree estimates from above and from below for the tight closure of a homogeneous R+-primary ideal in a two-dimensional normal standard-graded algebra R in terms of the minimal and the maximal slope of the sheaf of relations for some ideal generators. If moreover this sheaf of relations is semistable, then both degree estimates coincide and we get a vanishing type theorem.