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Faces of generalized cluster complexes and noncrossing partitions

E. Tzanaki
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Abstract

Let $Φ$ be an finite root system with corresponding reflection group $W$ and let $m$ be a nonnegative integer. We consider the generalized cluster complex $Δ^m(Φ)$ defined by S. Fomin and N. Reading and the poset $NC_{(m)}(W)$ of $m$-divisible noncrossing partitions defined by D. Armstrong. We give a characterization of the faces of $Δ^m(Φ)$ in terms of $NC_{(m)}(W)$, generalizing that of T. Brady and C. Watt given in the case $m=1$. Making use of this, we give a case free proof of a conjecture of F. Chapoton and D. Armstrong, which relates a certain refined face count of $Δ^m(Φ)$ with the Möbius function of $NC_{(m)}(W)$.

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E. Tzanaki. 2006-07-10. Faces of generalized cluster complexes and noncrossing partitions. https://arxiv.org/abs/math/0605785

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