A note on balanced bipartitions

نویسندگان

  • Baogang Xu
  • Juan Yan
  • Xingxing Yu
چکیده

A balanced bipartition of a graph G is a bipartition V1 and V2 of V (G) such that −1 ≤ |V1| − |V2| ≤ 1. Bollobás and Scott conjectured that if G is a graph with m edges and minimum degree at least 2 then G admits a balanced bipartition V1, V2 such that max{e(V1), e(V2)} ≤ m/3, where e(Vi) denotes the number of edges of G with both ends in Vi. In this note, we prove this conjecture for graphs with average degree at least 6 or with minimum degree at least 5. Moreover, we show that if G is a graph with m edges and n vertices, and if the maximum degree ∆(G) = o(n) or the minimum degree δ(G) → ∞, then G admits a balanced bipartition V1, V2 such that max{e(V1), e(V2)} ≤ (1+ o(1))m/4, answering a question of Bollobás and Scott in the affirmative. We also provide a sharp lower bound on max{e(V1, V2) : V1, V2 is a balanced bipartition of G}, in terms of size of a maximum matching, where e(V1, V2) denotes the number of edges between V1 and V2.

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عنوان ژورنال:
  • Discrete Mathematics

دوره 310  شماره 

صفحات  -

تاریخ انتشار 2010