论文标题
三角形的多转换和Tuza的猜想
Multi-transversals for Triangles and the Tuza's Conjecture
论文作者
论文摘要
在本文中,我们研究了关于三角形的主要和双重关系:对于任何图$ g $,让$ν(g)$是$ g $中的边缘 - 二十一个三角形的最大数量,而$τ(g)$是最小子集$ f $ f $ f $ f $ f $ f $ f $ g \ g \ setminus f $ triangle as triangle as triangle-free。很容易看出,$ν(g)\ leqτ(g)\ leq3ν(g)$,实际上,这种相当明显的不平等能够实现$ k $ - hyper匹配和覆盖超读物中的更一般的原始偶尔关系。图扎(Tuza)以1981美元的价格猜想,$τ(g)\ leq2ν(g)$,这个问题在离散数学方面的各个研究人员都受到了关注,解决了各种特殊情况,例如平面图,并将其推广到有限的最大平均度图,某些次要的无用图案,某些次要图形和非常密集的图形。尽管做出了这些努力,但一般图中的猜想仍在近四十年中保持开放。 在本文中,我们提供了猜想的非平凡后果的证明。也就是说,对于每$ k \ geq 2 $ \ leq2kν(g)$,使$ g $中的每个三角形至少$ k $ ements $ f $。我们的结果可以看作是Krivelevich在Tuza的猜想的分数版本上的结果的加强陈述(我们给出了一些说明这一点的例子。)我们结果的主要技术成分是一个充电论点,该论点是基于包装解决方案本地视图的$ F $中本地标识的$ f $。这个想法可能在进一步研究总体上,尤其是Tuza的猜想的过程中很有用。
In this paper, we study a primal and dual relationship about triangles: For any graph $G$, let $ν(G)$ be the maximum number of edge-disjoint triangles in $G$, and $τ(G)$ be the minimum subset $F$ of edges such that $G \setminus F$ is triangle-free. It is easy to see that $ν(G) \leq τ(G) \leq 3 ν(G)$, and in fact, this rather obvious inequality holds for a much more general primal-dual relation between $k$-hyper matching and covering in hypergraphs. Tuza conjectured in $1981$ that $τ(G) \leq 2 ν(G)$, and this question has received attention from various groups of researchers in discrete mathematics, settling various special cases such as planar graphs and generalized to bounded maximum average degree graphs, some cases of minor-free graphs, and very dense graphs. Despite these efforts, the conjecture in general graphs has remained wide open for almost four decades. In this paper, we provide a proof of a non-trivial consequence of the conjecture; that is, for every $k \geq 2$, there exist a (multi)-set $F \subseteq E(G): |F| \leq 2k ν(G)$ such that each triangle in $G$ overlaps at least $k$ elements in $F$. Our result can be seen as a strengthened statement of Krivelevich's result on the fractional version of Tuza's conjecture (and we give some examples illustrating this.) The main technical ingredient of our result is a charging argument, that locally identifies edges in $F$ based on a local view of the packing solution. This idea might be useful in further studying the primal-dual relations in general and the Tuza's conjecture in particular.