کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4598845 1631108 2015 31 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
More nonexistence results for symmetric pair coverings
ترجمه فارسی عنوان
نتایج غیرواقعی بیشتری برای پوشاندن جفت های متقارن
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات اعداد جبر و تئوری
چکیده انگلیسی

A (v,k,λ)(v,k,λ)-covering is a pair (V,B)(V,B), where V is a v  -set of points and BB is a collection of k-subsets of V (called blocks), such that every unordered pair of points in V is contained in at least λ   blocks in BB. The excess of such a covering is the multigraph on vertex set V in which the edge between vertices x and y   has multiplicity rxy−λrxy−λ, where rxyrxy is the number of blocks which contain the pair {x,y}{x,y}. A covering is symmetric if it has the same number of blocks as points. Bryant et al. [4] adapted the determinant related arguments used in the proof of the Bruck–Ryser–Chowla Theorem to establish the nonexistence of certain symmetric coverings with 2-regular excesses. Here, we adapt the arguments related to rational congruence of matrices and show that they imply the nonexistence of some cyclic symmetric coverings and of various symmetric coverings with specified excesses.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Linear Algebra and its Applications - Volume 487, 15 December 2015, Pages 43–73
نویسندگان
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