کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4646957 1342320 2015 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Frustrated triangles
ترجمه فارسی عنوان
مثلث ناخوشایند
کلمات کلیدی
مثلث ناخوشایند، سرخوردگی هندسی
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات ریاضیات گسسته و ترکیبات
چکیده انگلیسی

A triple of vertices in a graph is a frustrated triangle   if it induces an odd number of edges. We study the set Fn⊂[0,(n3)] of possible number of frustrated triangles f(G)f(G) in a graph GG on nn vertices. We prove that about two thirds of the numbers in [0,n3/2][0,n3/2] cannot appear in FnFn, and we characterise the graphs GG with f(G)∈[0,n3/2]f(G)∈[0,n3/2]. More precisely, our main result is that, for each n≥3n≥3, FnFn contains two interlacing sequences 0=a0≤b0≤a1≤b1≤⋯≤am≤bm∼n3/20=a0≤b0≤a1≤b1≤⋯≤am≤bm∼n3/2 such that Fn∩(bt,at+1)=0̸Fn∩(bt,at+1)=0̸ for all tt, where the gaps are |bt−at+1|=(n−2)−t(t+1)|bt−at+1|=(n−2)−t(t+1) and |at−bt|=t(t−1)|at−bt|=t(t−1). Moreover, f(G)∈[at,bt]f(G)∈[at,bt] if and only if GG can be obtained from a complete bipartite graph by flipping exactly tt edges/nonedges. On the other hand, we show, for all nn sufficiently large, that if m∈[f(n),(n3)−f(n)], then m∈Fnm∈Fn where f(n)f(n) is asymptotically best possible with f(n)∼n3/2f(n)∼n3/2 for nn even and f(n)∼2n3/2 for nn odd. Furthermore, we determine the graphs with the minimum number of frustrated triangles amongst those with nn vertices and e≤n2/4e≤n2/4 edges.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Discrete Mathematics - Volume 338, Issue 12, 6 December 2015, Pages 2363–2373
نویسندگان
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