Stack-sorting with Stacks Avoiding Vincular Patterns

TL;DR

This paper introduces a new stack-sorting map avoiding vincular patterns, characterizes the sorted permutation classes, and explores properties like maximum preimage size and periodic points, extending previous pattern-avoidance sorting frameworks.

Contribution

It defines and analyzes a novel vincular pattern-avoiding stack-sorting map, characterizes sorted classes for specific patterns, and investigates key dynamical properties.

Findings

Characterized and enumerated sorting classes for seven length 3 patterns.

Determined when sorting classes form permutation classes.

Computed maximum preimage sizes and identified periodic points.

Abstract

We introduce the stack-sorting map $\text{SC}_\sigma$ that sorts, in a right-greedy manner, an input permutation through a stack that avoids some vincular pattern $\sigma$. The stack-sorting maps of Cerbai et al. in which the stack avoids a pattern classically and Defant and Zheng in which the stack avoids a pattern consecutively follow as special cases. We first characterize and enumerate the sorting class $\text{Sort}(\text{SC}_\sigma)$, the set of permutations sorted by $s\circ\text{SC}_\sigma$, for seven length $3$ patterns $\sigma$. We also decide when $\text{Sort}(\text{SC}_\sigma)$ is a permutation class. Next, we compute $\max_{\pi\in \mathfrak S_n}|\text{SC}_\sigma^{-1}(\pi)|$ and characterize the periodic points of $\text{SC}_\sigma$ for several length $3$ patterns $\sigma$. We end with several conjectures and open problems.