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arXiv 1104.4669cs.DS
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在有界路宽图中寻找轻生成子

Finding Light Spanners in Bounded Pathwidth Graphs

Michelangelo Grigni, Hao-Hsiang Hung

摘要:

给定一个边权图$G$和$ε>0$,一个$(1+ε)$ -图是一个生成子图$G'$,它的最短路距离在一个$(1+ε)$因子内近似于$G$的最短路距离。如果$G$来自某些次闭图族(至少是有界亏格图和顶点图),则我们知道存在轻空间。也就是说,我们可以计算一个$(1+ε)$ -最小生成树的总边权重至多为一个常数乘以最小生成树的权重的$G'$ $G'$。这个常数可以取决于$ε$和图形族,但不取决于特定的图形$G$,也不取决于其边权重。对于几个次闭图族中的加权图,轻空间的存在性在度量TSP(旅行商问题)和一些类似问题的逼近方案设计中是必不可少的.本文对关于每一个次闭图族都存在光空间的猜想作了一些进展。特别是,我们证明了它们存在的图有界路宽。我们这样做,通过建设足够轻的单调生成树在这样的图。

英文摘要:

Given an edge-weighted graph $G$ and $ε>0$, a $(1+ε)$-spanner is a spanning subgraph $G'$ whose shortest path distances approximate those of $G$ within a $(1+ε)$ factor. If $G$ is from certain minor-closed graph families (at least bounded genus graphs and apex graphs), then we know that light spanners exist. That is, we can compute a $(1+ε)$-spanner $G'$ with total edge weight at most a constant times the weight of a minimum spanning tree. This constant may depend on $ε$ and the graph family, but not on the particular graph $G$ nor on its edge weighting. For weighted graphs from several minor-closed graph families, the existence of light spanners has been essential in the design of approximation schemes for the metric TSP (the traveling salesman problem) and some similar problems. In this paper we make some progress towards the conjecture that light spanners exist for every minor-closed graph family. In particular, we show that they exist for graphs with bounded pathwidth. We do this via the construction of light enough monotone spanning trees in such graphs.

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