کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4587411 1334143 2009 24 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Quasilength, latent regular sequences, and content of local cohomology
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات اعداد جبر و تئوری
پیش نمایش صفحه اول مقاله
Quasilength, latent regular sequences, and content of local cohomology
چکیده انگلیسی

The quasilength of a finitely generated module that is killed by a power of a finitely generated ideal I is introduced: it is the length of a shortest filtration of the module with factors that are cyclic modules killed by I. This notion is then used to define a notion of content for the dth local cohomology module of a ring or module with support in an ideal generated by d elements. In the case of a ring, which is central, this content is a real number between 0 and 1. It is not known whether it is independent of the choice of the d generators nor whether it can change if the generators are replaced by powers. In positive prime characteristic it is shown that the content is always 0 or 1. This is an open question in equal characteristic 0 and in mixed characteristic. It is conjectured that if the elements form a system of parameters in a local ring of dimension d, then the content is 1. This is proved if the ring contains a field. In mixed characteristic it is an open question in dimension 3 or more, and implies the direct summand conjecture. The relationship between the notions of quasilength and content and the property that a sequence of elements can become a regular sequence on a ring or module after base change is explored.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Algebra - Volume 322, Issue 9, 1 November 2009, Pages 3170-3193