Cells and cacti

TL;DR

This paper constructs an action of the cactus group on Coxeter groups that respects cell partitions, depending on a weight function, extending understanding of symmetries in algebraic structures.

Contribution

It introduces a new action of the cactus group on Coxeter groups that aligns with cell partitions, influenced by a weight function, under specific conditions.

Findings

Action respects cell partitions under certain hypotheses

Dependence on weight function $ extphi$ is significant

Applicable to finite Coxeter groups of rank less than 5

Abstract

Let $(W,S)$ be a Coxeter system, let $\varphi$ be a weight function on $S$ and let ${\mathrm{Cact}}\_W$ denote the associated {\it cactus group}. Following an idea of I. Losev, we construct an action of ${\mathrm{Cact}}\_W \times {\mathrm{Cact}}\_W$ on $W$ which has nice properties with respect to the partition of $W$ into left, right or two-sided cells (under some hypothesis, which hold for instance if $\varphi$ is constant or if $W$ is finite of rank $\textless{} 5$). It must be noticed that the action depends heavily on $\varphi$.