设G是一个没有4-圈的平面图,G的平方图G^2定义在V(G)上,使得2个点u和v在G^2中是相邻的当且仅当它们在G中的距离为1或2.证明了:δ(G^2)≤△(G)+33,并且当δ(G)〉14时有δ(G^2)≤16.其中,δ(H)和△(H)分别表示图H的最小度和最大度.
Let G be a planar graph without 4-cycles. The square G^2 of G is the graph defined on the vertex set V( G) such that two vertices u and v are adjacent in G: if and only if they are at distance 1 or 2 in G. It was proved that δ ( G^2)≤ Δ ( G ) + 33, δ( G^2) ≤ 16 when δ ( G ) ≥4. Here δ ( H ) and Δ ( H ) denoted the minimum degree and the maximum degree of a graph H, respectively.