发表机构
Harvard University(哈佛大学)
机构由 AI 辅助整理,请以论文原文为准。AI 中文总结
本文完整枚举了避免两个模式的平移不变全序,并构造了312-避免TITO与非交叉弧图双射的逆,扩展了组合框架。
AI 中文摘要
设 $n$ 为正整数。周期为 $n$ 的平移不变全序(TITO)是整数集上的一种全序,它在 $n$ 的倍数平移下保持不变。这些结构在 Coxeter 群的研究中自然出现。特别地,实 $n$-TITO 与仿射对称群 $\widetilde S_n$ 的正根系的双闭集之间存在双射。Barkley 和 Defant 最近引入了 TITO 的模式避免概念,并利用它定义了仿射 Tamari 格。避免单个长度为 $3$ 的模式的 TITO 的枚举归功于 Crites 和 Barkley--Defant。我们将这项工作扩展到避免两个模式的 TITO。我们的主要结果包括对避免 $S_3\times S_3$ 中一对模式的 TITO 的完整枚举,以及对避免一对 $(p, q)$(其中 $p \in S_3 \setminus \{123, 321\}$,$q \in S_4$)的 TITO 的完整枚举。此外,我们提供了 $312$-避免 TITO 与非交叉弧图之间双射的逆的显式构造,从而扩展了 Barkley 引入的组合框架。
英文摘要
Let $n$ be a positive integer. A translation-invariant total order (TITO) with period $n$ is a total order of the integers that is invariant under translations by multiples of $n$. These structures arise naturally in the study of Coxeter groups. In particular, real $n$-TITOs are in bijection with biclosed sets of positive roots of the affine symmetric group $\widetilde S_n$. Barkley and Defant recently introduced pattern avoidance for TITOs and used it to define the affine Tamari lattice. The enumeration of TITOs avoiding a single pattern of length $3$ is due to Crites and Barkley--Defant. We extend this work to TITOs avoiding two patterns. Our main results include a complete enumeration of TITOs that avoid a pair of patterns in $S_3\times S_3$, as well as of TITOs that avoid a pair $(p, q)$ with $p \in S_3 \setminus \{123, 321\}$ and $q \in S_4$. Furthermore, we provide an explicit construction of the inverse of the bijection between $312$-avoiding TITOs and noncrossing arc diagrams, thereby extending the combinatorial framework introduced by Barkley.