کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4656403 1343435 2008 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Erdős–Ko–Rado theorems for permutations and set partitions
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات ریاضیات گسسته و ترکیبات
پیش نمایش صفحه اول مقاله
Erdős–Ko–Rado theorems for permutations and set partitions
چکیده انگلیسی

Let Sym([n]) denote the collection of all permutations of [n]={1,…,n}. Suppose A⊆Sym([n]) is a family of permutations such that any two of its elements (when written in its cycle decomposition) have at least t cycles in common. We prove that for sufficiently large n, |A|⩽(n−t)! with equality if and only if A is the stabilizer of t fixed points. Similarly, let B(n) denote the collection of all set partitions of [n] and suppose A⊆B(n) is a family of set partitions such that any two of its elements have at least t blocks in common. It is proved that, for sufficiently large n, |A|⩽Bn−t with equality if and only if A consists of all set partitions with t fixed singletons, where Bn is the nth Bell number.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Combinatorial Theory, Series A - Volume 115, Issue 6, August 2008, Pages 1008-1020