Involution Products in Coxeter Groups


For $W$ a Coxeter group, let $\mathcal{W} = \{ w \in W \;| \; w = xy \; \mbox{where} \; x, y \in W \; \mbox{and} \; x^2 = 1 = y^2 \}$. If $W$ is finite, then it is well known that $W = \mathcal{W}$. Suppose that $w \in \mathcal{W}$. Then the minimum value of $\ell(x) + \ell(y) - \ell(w)$, where $x, y \in W$ with $w = xy$ and $x^2 = 1 = y^2$, is called the \textit{excess} of $w$ ($\ell$ is the length function of $W$). The main result established here is that $w$ is always $W$-conjugate to an element with excess equal to zero.Comment: This is the preprint version. We also include, on the final page, a short Corrigendum correcting an error in Theorem 1.1. We are grateful to the referee of a later paper for pointing this out. The Corrigendum appeared as "Corrigendum to Involution products in Coxeter groups [J. Group Theory 14 (2011), no. 2, 251--259]" in J. Group Theory 17 (2014), no. 2, 379--38

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