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The complexity of perfect matchings and packings in dense hypergraphs
Journal of Combinatorial Theory Series B ( IF 1.2 ) Pub Date : 2019-07-19 , DOI: 10.1016/j.jctb.2019.06.004
Jie Han , Andrew Treglown

Given two k-graphs H and F, a perfect F-packing in H is a collection of vertex-disjoint copies of F in H which together cover all the vertices in H. In the case when F is a single edge, a perfect F-packing is simply a perfect matching. For a given fixed F, it is often the case that the decision problem whether an n-vertex k-graph H contains a perfect F-packing is NP-complete. Indeed, if k3, the corresponding problem for perfect matchings is NP-complete [17], [7] whilst if k=2 the problem is NP-complete in the case when F has a component consisting of at least 3 vertices [14].

In this paper we give a general tool which can be used to determine classes of (hyper)graphs for which the corresponding decision problem for perfect F-packings is polynomial time solvable. We then give three applications of this tool: (i) Given 1k1, we give a minimum -degree condition for which it is polynomial time solvable to determine whether a k-graph satisfying this condition has a perfect matching; (ii) Given any graph F we give a minimum degree condition for which it is polynomial time solvable to determine whether a graph satisfying this condition has a perfect F-packing; (iii) We also prove a similar result for perfect K-packings in k-graphs where K is a k-partite k-graph.

For a range of values of ,k (i) resolves a conjecture of Keevash, Knox and Mycroft [20]; (ii) answers a question of Yuster [47] in the negative; whilst (iii) generalises a result of Keevash, Knox and Mycroft [20]. In many cases our results are best possible in the sense that lowering the minimum degree condition means that the corresponding decision problem becomes NP-complete.



中文翻译:

稠密超图的完美匹配和堆积的复杂性

给定两个ķ -graphs ^ h˚F,完美˚F在分装^ h是顶点不相交的副本的集合˚F^ h一起覆盖所有顶点^ h。在F是单边的情况下,完美的F包装只是完美的匹配。对于给定的固定F,通常情况下,n-顶点kH是否包含理想F堆积的决策问题是NP完全的。确实,如果ķ3,则完美匹配的相应问题是NP完全[17],[7],而如果 ķ=2F的分量至少由3个顶点组成时,问题是NP完全的[14]。

在本文中,我们提供了一种通用工具,可用于确定(超)图的类,对于这些类,理想的F堆积的相应决策问题是多项式时间可解的。然后,我们给出该工具的三个应用:(i)给定1个ķ-1个,我们给出一个最小度条件,对于该条件,可以通过多项式时间来确定满足该条件的k图是否具有完美匹配;(ii)给定任何图F,我们给出一个最小次数条件,对于该条件,可以确定多项式时间,以确定满足该条件的图是否具有理想的F堆积;(三)我们还证明了完美类似的结果ķ在-packings ķ -graphs其中ķķ -partite ķ -图。

对于以下范围的值 ķ(i)解决了Keevash,Knox和Mycroft的猜想[20];(ii)否定回答Yuster [47]的问题;(iii)概括了Keevash,Knox和Mycroft的结果[20]。在许多情况下,从降低最低程度条件意味着相应的决策问题变为NP完全的意义上说,我们的结果是最好的。

更新日期:2019-07-19
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