论文标题

顶点分区分为一个独立的集合和一个森林,每个组成部分小

Vertex Partitions into an Independent Set and a Forest with Each Component Small

论文作者

Cranston, Daniel W., Yancey, Matthew P.

论文摘要

对于每个整数k> = 2,我们确定对疯狂(g)的尖锐绑定,以便可以将v(g)划分为i和f_k集,其中i是一个独立的集合,g [f_k]是每个组件在最多具有k个顶点的森林。对于每个K,我们构建了一个无限的例子,显示我们的结果是最好的。我们的结果表明,每个平面图G的每个平面图至少9(分别为8,7)都将V(g)分配到独立的集合I和A集合中,使G [F]是一个最多有秩序的森林,最多3(resp。4,6)。 亨德里(Hendrey),诺林(Norin)和伍德(Wood)要求最大的函数g(a,b),以便如果疯狂(g)<g(a,b),那么v(g)将a和b分配为a和b,以使得疯狂(g [a])<a和mad(g [b])<b。他们特别要求G(1,b)的值,即A是独立集的情况。以前,唯一已知的值是G(1,4/3)和G(1,2)。每当4/3 <b <2时,我们都会发现g(1,b)。

For each integer k >= 2, we determine a sharp bound on mad(G) such that V(G) can be partitioned into sets I and F_k, where I is an independent set and G[F_k] is a forest in which each component has at most k vertices. For each k we construct an infinite family of examples showing our result is best possible. Our results imply that every planar graph G of girth at least 9 (resp. 8, 7) has a partition of V(G) into an independent set I and a set F such that G[F] is a forest with each component of order at most 3 (resp. 4, 6). Hendrey, Norin, and Wood asked for the largest function g(a,b) such that if mad(G) < g(a,b) then V(G) has a partition into sets A and B such that mad(G[A]) < a and mad(G[B]) < b. They specifically asked for the value of g(1,b), i.e., the case when A is an independent set. Previously, the only values known were g(1,4/3) and g(1,2). We find g(1,b) whenever 4/3 < b < 2.

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