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arXiv 2601.18565math.CO
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稠密图中无大独立集的单色三角形铺砌

Monochromatic triangle-tilings in dense graphs without large independent sets

University of Science and Technology of China(中国科学技术大学);Hefei National Laboratory, University of Science and Technology of China(合肥国家实验室,中国科学技术大学)

Xinmin Hou, Xiangyang Wang, Zhi Yin

AI总结:

本文研究了稠密图中无大独立集的2边着色图的弱单色三角形铺砌问题,给出了渐近最优的铺砌大小阈值。

摘要:

给定两个图H和G,H-铺砌是G中一组不相交的H的副本的家族。一个完美H-铺砌覆盖G的所有顶点。Corradi-Hajnal定理(1963)指出,一个有n个顶点的图G,若最小度δ(G)≥2n/3,则包含一个完美三角形铺砌。对于一个有n个顶点的图G,其独立数α(G)=o(n),Balogh、Molla和Sharifzadeh(Random Structures & Algorithms,2016)证明,当最小度为(1/2+o(1))n时,强制一个完美三角形铺砌。在2边着色图中,Balogh、Freschi和Treglown(European J. Combin. 2026)确定了强制强或弱单色三角形铺砌覆盖规定比例顶点的最小度阈值:强铺砌要求所有三角形在同一颜色类中,而弱铺砌仅要求每个三角形单色。在本文中,我们结合这两条研究线的条件,并证明,对于任意一个有n个顶点的2边着色图G,若α(G)=o(n),则包含一个弱单色三角形铺砌Γ,其大小为 |Γ|≥ \begin{cases} 2δ(G)-n-o(n), & \text{如果 }\frac12 n≤δ(G)≤\frac35 n,\[2mm] δ(G)/3-o(n), & \text{如果 }δ(G)>\frac35 n. \end{cases} 两个界都是渐近最优的。我们在证明中使用了度数形式正则性引理。

英文摘要:

Given two graphs $H$ and $G$, an $H$-tiling is a family of vertex-disjoint copies of $H$ in $G$. A perfect $H$-tiling covers all vertices of $G$. The Corradi-Hajnal theorem (1963) states that an $n$-vertex graph $G$ with minimum degree $δ(G)\ge 2n/3$ contains a perfect triangle-tiling. For an $n$-vertex graph $G$ with independence number $α(G)=o(n)$, Balogh, Molla and Sharifzadeh (Random Structures & Algorithms, 2016) showed that a minimum degree of $(\frac12+o(1))n$ forces a perfect triangle-tiling. In a 2-edge-colored graph, Balogh, Freschi, Treglown (European J. Combin. 2026) determined the (asymptotic) minimum degree threshold for forcing a strong or weak monochromatic triangle-tiling covering a prescribed proportion of the vertices: a strong tiling requires all triangles to be in the same color class, while a weak tiling only requires each triangle to be monochromatic. In this paper, we combine the conditions from these two lines of work and prove that every $2$-edge-colored $n$-vertex graph $G$ with $α(G)=o(n)$ contains a weak monochromatic triangle-tiling $Γ$ of size \[ |Γ|\ge \begin{cases} 2δ(G)-n-o(n), & \text{if }\frac12 n\le δ(G)\le \frac35 n,\\[2mm] δ(G)/3-o(n), & \text{if }δ(G)>\frac35 n. \end{cases} \] Both bounds are asymptotically optimal. We use the degree form regularity lemma in our proof.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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