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arXiv · 2505.21718

Garside shadows and biautomatic structures in Coxeter groups

Fabricio Dos Santos
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Abstract

In 2022, Osajda and Przytycki showed that any Coxeter group $W$ is biautomatic. Key to their proof is the notion of voracious projection of an element $g \in W$, which is used iteratively to construct a biautomatic structure for $W$: the voracious language. In this article, we generalize these two notions by defining them for any Garside shadow $B$ in a Coxeter system $(W,S)$. This leads to the result that any finite Garside shadow in $(W,S)$ can be used to construct a biautomatic structure for $W$. In addition, we show that for the Garside shadow $L$ of low elements, the biautomatic structure obtained corresponds to the original voracious language of Osajda and Przytycki. These results answer a question of Hohlweg and Parkinson.

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Fabricio Dos Santos. 2025-05-27. Garside shadows and biautomatic structures in Coxeter groups. https://arxiv.org/abs/2505.21718

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