Polygon dissections and some generalizations of cluster complexes
Abstract
Description
Let $W$ be a Weyl group corresponding to the root system $A_{n-1}$ or $B_n$.
We define a simplicial complex $ Δ^m_W $ in terms of polygon dissections for such a group and any positive integer $m$. For $ m=1 $, $ Δ^m_W$ is isomorphic to the cluster complex corresponding to $ W $, defined in \cite{FZ}. We enumerate the faces of $ Δ^m_W $ and show that the entries of its $h$-vector are given by the generalized Narayana numbers $ N^m_W(i) $, defined in \cite{Atha3}. We also prove that for any $ m \geq 1$ the complex $ Δ^m_W $ is shellable and hence Cohen-Macaulay.
9 pages, 3 figures, the type D case has been removed, some corrections on the proof of Theorem 3.1 have been made. To appear in JCTA
9 pages, 3 figures, the type D case has been removed, some corrections on the proof of Theorem 3.1 have been made. To appear in JCTA