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On the Oberwolfach problem for single-flip 2-factors via graceful labelings
Journal of Combinatorial Theory Series A ( IF 1.1 ) Pub Date : 2022-03-08 , DOI: 10.1016/j.jcta.2022.105611
A.C. Burgess 1 , P. Danziger 2 , T. Traetta 3
Affiliation  

Let F be a 2-regular graph of order v. The Oberwolfach problem OP(F), posed in 1967 and still open, asks for a decomposition of Kv into copies of F. In this paper we show that OP(F) has a solution whenever F has a sufficiently large cycle which meets a given lower bound and, in addition, has a single-flip automorphism, which is an involutory automorphism acting as a reflection on exactly one of the cycles of F. Furthermore, we prove analogous results for the minimum covering version and the maximum packing version of the problem. We also show a similar result when the edges of Kv have multiplicity 2, but in this case we do not require that F be single-flip.

Our approach allows us to explicitly construct solutions to the Oberwolfach Problem with well-behaved automorphisms, in contrast with some recent asymptotic results, based on probabilistic methods, which are nonconstructive and do not provide a lower bound on the order of F that guarantees the solvability of OP(F).

Our constructions are based on a doubling construction which applies to graceful labelings of 2-regular graphs with a vertex removed. We show that this class of graphs is graceful as long as the length of the path-component is sufficiently large. A much better lower bound on the length of the path is given for an α-labeling of such graphs to exist.



中文翻译:

关于通过优雅标记的单翻转 2 因子的 Oberwolfach 问题

Fv阶的 2 正则图。奥伯沃尔法赫问题(F),于 1967 年提出并仍然开放,要求分解ķvF的副本。在本文中,我们表明(F)只要F具有满足给定下限的足够大的循环,并且此外,具有单翻转自同构,它是一个对合自同构,它恰好反映了F的一个循环。此外,我们证明了问题的最小覆盖版本和最大打包版本的类似结果。当边缘ķv有多重性 2,但在这种情况下,我们不要求F是单次翻转的。

我们的方法允许我们用表现良好的自同构显式构造 Oberwolfach 问题的解决方案,这与最近基于概率方法的一些渐近结果相反,这些结果是非构造性的,并且不提供F阶的下限来保证可解性的(F).

我们的构造基于一个加倍构造,该构造适用于删除顶点的 2 正则图的优雅标记。我们证明,只要路径分量的长度足够大,这类图是优雅的。对于存在的此类图的α标记,给出了路径长度的更好的下限。

更新日期:2022-03-08
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