کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4657466 | 1343739 | 2006 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Obstructions to branch-decomposition of matroids
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موضوعات مرتبط
مهندسی و علوم پایه
ریاضیات
ریاضیات گسسته و ترکیبات
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
A (δ,γ)-net in a matroid M is a pair (N,P) where N is a minor of M, P is a set of series classes in N, |P|⩾δ, and the pairwise connectivity, in M, between any two members of P is at least γ. We prove that, for any finite field F, nets provide a qualitative characterization for branch-width in the class of F-representable matroids. That is, for an F-representable matroid M, we prove that: (1) if M contains a (δ,γ)-net where δ and γ are both very large, then M has large branch-width, and, conversely, (2) if the branch-width of M is very large, then M or M∗ contains a (δ,γ)-net where δ and γ are both large.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Combinatorial Theory, Series B - Volume 96, Issue 4, July 2006, Pages 560-570
Journal: Journal of Combinatorial Theory, Series B - Volume 96, Issue 4, July 2006, Pages 560-570