AI中文摘要
设$r,s,t\geq2$为整数。对于$r$-图$G$和$F_1,\dots,F_s$,如果$G$的每个$s$-边染色都产生一个第$i$种颜色的单色副本$F_i$(对某个$1\leq i\leq s$),则记$G\to(F_1,\dots,F_s)$。令$\mathcal{R}(F_1,\dots,F_s)$表示所有满足$G\to(F_1,\dots,F_s)$的$r$-图$G$的族。当$F_1=\dots=F_s=F$时,记$\mathcal{R}(F;s)=\mathcal{R}(F_1,\dots,F_s)$。 本文研究何时$\mathcal{R}(H;s)\subseteq\mathcal{R}(Q_1,\dots,Q_t)$成立,其中$H=H^{(r)}(n,p)$是随机$r$-图,$Q_1,\dots,Q_t$是固定的$r$-图。我们的主要结果确定了一大类这样的$Q_1,\dots,Q_t$(包括完全$r$-图)的阈值。证明的关键要素是推广了Graham、Łuczak、Rödl和Ruciński的一个结果,该结果为$\mathcal{R}(F_1,\dots,F_s)\subseteq\mathcal{R}(Q_1,\dots,Q_t)$提供了充要条件,其中$Q_1,\dots,Q_t$是高度连通的。作为副产品,我们刻画了何时两个高度连通的$r$-图元组是Ramsey等价的。
英文摘要
Let $r,s,t\geq2$ be integers. For $r$-graphs $G$ and $F_1,\dots,F_s$, we write $G\to(F_1,\dots,F_s)$ if every $s$-edge-coloring of $G$ yields a monochromatic copy of $F_i$ in the $i$-th color for some $1\leq i\leq s$. Let $\mathcal{R}(F_1,\dots,F_s)$ denote the family of all $r$-graphs $G$ with $G\to(F_1,\dots,F_s)$. When $F_1=\dots=F_s=F$, we write $\mathcal{R}(F;s)=\mathcal{R}(F_1,\dots,F_s)$.
In this paper, we investigate when $\mathcal{R}(H;s)\subseteq\mathcal{R}(Q_1,\dots,Q_t)$ holds, where $H=H^{(r)}(n,p)$ is a random $r$-graph and $Q_1,\dots,Q_t$ are fixed $r$-graphs. Our main result determines the threshold for a large class of such $Q_1,\dots,Q_t$, including complete $r$-graphs. The key ingredient in our proof is a generalization of a result of Graham, Łuczak, Rödl, and Ruciński, which provides a necessary and sufficient condition for $\mathcal{R}(F_1,\dots,F_s)\subseteq\mathcal{R}(Q_1,\dots,Q_t)$, where $Q_1,\dots,Q_t$ are highly connected. As a byproduct, we characterize when two tuples of highly connected $r$-graphs are Ramsey equivalent.