论文标题

关于对和弦图的缩写的参数化近似性

On the Parameterized Approximability of Contraction to Classes of Chordal Graphs

论文作者

Gunda, Spoorthy, Jain, Pallavi, Lokshtanov, Daniel, Saurabh, Saket, Tale, Prafullkumar

论文摘要

{\ em Contracts Edges}的图形操作是图形理论中的基本操作之一。通过收缩$ k $边缘,通过收缩$ k $边缘编辑的参数化复杂性最近引起了大量的科学关注,并获得了一些新的结果。事实证明,一些重要的图形家庭,即在边缘收缩的背景下,在边缘收缩的背景下,弦图的亚家族比人们预期的要困难得多。在本文中,我们研究\ textsc {$ \ cal f $ -contraction}问题,其中$ \ cal f $是弦式图的亚家族,在参数化近似领域中。形式上,给定图形$ g $和一个整数$ k $,\ textsc {$ \ cal f $ -contraction}询问是否存在$ x \ subseteq e(g)$ \ leq k $。在这里,$ g/x $是通过$ x $收缩的边缘从$ g $获得的图表。我们获得了\ textsc {$ \ cal f $ -contraction}问题的以下结果。 $(1)$我们表明\ textsc {clique contraction}允许一个多项式尺寸近似内核化方案(\ textsf {psaks})。 $(2)$我们给出$(2+ε)$ - \ textsc {split Contraction}的近似多项式内核(这也意味着$(2+ε)$ - \ fpt-appRoximation算法\ textsc {splitscortaction})。此外,我们表明,假设\ textsf {gap-eth},没有$ \ left(\ frac {5} {4} {4} {4}-Δ\ right)$ - \ fpt-appRoximation算法\ textsc {split contraction}。在这里,$ε,δ> 0 $是固定常数。 $(3)$ \ textsc {chordal收缩}是\ wth。我们可以通过观察现有的\ textsf {w [2] - hardness}的补充来补充这一结果。在这里,$ f(k)$是一个任意功能,具体取决于$ k $。

A graph operation that {\em contracts edges} is one of the fundamental operations in the theory of graph minors. Parameterized Complexity of editing to a family of graphs by contracting $k$ edges has recently gained substantial scientific attention, and several new results have been obtained. Some important families of graphs, namely the subfamilies of chordal graphs, in the context of edge contractions, have proven to be significantly difficult than one might expect. In this paper, we study the \textsc{$\cal F$-Contraction} problem, where $\cal F$ is a subfamily of chordal graphs, in the realm of parameterized approximation. Formally, given a graph $G$ and an integer $k$, \textsc{ $\cal F$-Contraction} asks whether there exists $X \subseteq E(G)$ such that $G/X \in \cal F$ and $|X| \leq k$. Here, $G/X$ is the graph obtained from $G$ by contracting edges in $X$. We obtain the following results for the \textsc{ $\cal F$-Contraction} problem. $(1)$ We show that \textsc{Clique Contraction} admits a polynomial-size approximate kernelization scheme (\textsf{PSAKS}). $(2)$ We give a $(2+ε)$-approximate polynomial kernel for \textsc{Split Contraction} (which also implies a factor $(2+ε)$-\FPT-approximation algorithm for \textsc{ Split Contraction}). Furthermore, we show that, assuming \textsf{ Gap-ETH}, there is no $\left(\frac{5}{4}-δ\right)$-\FPT-approximation algorithm for \textsc{Split Contraction}. Here, $ε, δ>0$ are fixed constants. $(3)$ \textsc{Chordal Contraction} is known to be \WTH. We complement this result by observing that the existing \textsf{W[2]-hardness} reduction can be adapted to show that, assuming \FPT $\neq$ \textsf{W[1]}, there is no $F(k)$-\FPT-approximation algorithm for \textsc{Chordal Contraction}. Here, $F(k)$ is an arbitrary function depending on $k$ alone.

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