arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1608.05352math.CO
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有界直径荫度

Bounded Diameter Arboricity

Martin Merker, Luke Postle

摘要:

我们引入了\emph{bounded diameter arboricity}的概念。具体地,图的\emph{diameter-$d$ arboricity}是使得图的边可以被划分成$k$森林的最小数目$k$,每个$k$森林的分量具有至多$d$的直径。一类图具有有界直径荫度$k$,如果存在一个自然数$d$,使得该类图中的每个图至多具有直径- $d$荫度$k$ .我们猜想荫度至多为$k$的图类具有有界直径荫度至多为$k+1$ .我们证明了这个猜想$k\in \{2,3\}$证明了更强的断言,森林和星森林的工会可以划分成两个森林的直径最多为18。我们利用这些结果来刻画围长至少为$g$的平面图的有界直径荫度,对于所有$g\ne 5$。作为一个应用,我们证明了每个6-边连通平面(多)图都包含两个边不相交的$\frac{18}{19}$ -瘦生成树.

英文摘要:

We introduce the notion of \emph{bounded diameter arboricity}. Specifically, the \emph{diameter-$d$ arboricity} of a graph is the minimum number $k$ such that the edges of the graph can be partitioned into $k$ forests each of whose components has diameter at most $d$. A class of graphs has bounded diameter arboricity $k$ if there exists a natural number $d$ such that every graph in the class has diameter-$d$ arboricity at most $k$. We conjecture that the class of graphs with arboricity at most $k$ has bounded diameter arboricity at most $k+1$. We prove this conjecture for $k\in \{2,3\}$ by proving the stronger assertion that the union of a forest and a star forest can be partitioned into two forests of diameter at most 18. We use these results to characterize the bounded diameter arboricity for planar graphs of girth at least $g$ for all $g\ne 5$. As an application we show that every 6-edge-connected planar (multi)graph contains two edge-disjoint $\frac{18}{19}$-thin spanning trees.

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