کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4587608 1334151 2008 21 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Finite index supergroups and subgroups of torsionfree abelian groups of rank two
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات اعداد جبر و تئوری
پیش نمایش صفحه اول مقاله
Finite index supergroups and subgroups of torsionfree abelian groups of rank two
چکیده انگلیسی

Every torsionfree abelian group A of rank two is a subgroup of Q⊕Q and is expressed by a direct limit of free abelian groups of rank two with lower diagonal integer-valued 2×2-matrices as the bonding maps. Using these direct systems we classify all subgroups of Q⊕Q which are finite index supergroups of A or finite index subgroups of A. Using this classification we prove that for each prime p there exists a torsionfree abelian group A satisfying the following, where A⩽Q⊕Q and all supergroups are subgroups of Q⊕Q:(1)for each natural number s there are s-index supergroups and also s-index subgroups;(2)each pair of distinct s-index supergroups are non-isomorphic and each pair of distinct s-index subgroups are non-isomorphic.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Algebra - Volume 319, Issue 9, 1 May 2008, Pages 3567-3587