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arXiv · 1310.2378

Irrelevant Vertices for the Planar Disjoint Paths Problem

Isolde Adler·Stavros G. Kolliopoulos·Philipp Klaus Krause·Daniel Lokshtanov·Saket Saurabhh·Dimitrios M. Thilikos
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Abstract

The Disjoint Paths Problem asks, given a graph $G$ and a set of pairs of terminals $(s_{1},t_{1}),\ldots,(s_{k},t_{k})$, whether there is a collection of $k$ pairwise vertex-disjoint paths linking $s_{i}$ and $t_{i}$, for $i=1,\ldots,k.$ In their $f(k)\cdot n^{3}$ algorithm for this problem, Robertson and Seymour introduced the irrelevant vertex technique according to which in every instance of treewidth greater than $g(k)$ there is an "irrelevant" vertex whose removal creates an equivalent instance of the problem. This fact is based on the celebrated Unique Linkage Theorem, whose - very technical - proof gives a function $g(k)$ that is responsible for an immense parameter dependence in the running time of the algorithm. In this paper we give a new and self-contained proof of this result that strongly exploits the combinatorial properties of planar graphs and achieves $g(k)=O(k^{3/2}\cdot 2^{k}).$ Our bound is radically better than the bounds known for general graphs.

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Isolde Adler, Stavros G. Kolliopoulos, Philipp Klaus Krause, Daniel Lokshtanov, Saket Saurabhh, Dimitrios M. Thilikos. 2013-10-09. Irrelevant Vertices for the Planar Disjoint Paths Problem. https://arxiv.org/abs/1310.2378

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