The Weyl group of $\frak{g}_2$ is the dihedral $D_6$. Let us denote its longest element by $w_0$. How many reduced decompositions does $w_0$ have?
1 Answer
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The weak order of a dihedral group looks like a polygon (see e.g. Figure 3.1 in the book "Combinatorics of Coxeter groups" by Björner and Brenti). Hence there are 2 reduced decompositions of $w_0$ (= maximal chains from bottom to top) in these cases.
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$\begingroup$ See also findstat.org/StatisticsDatabase/St001585 $\endgroup$ Commented Jan 15, 2022 at 15:00