Fan realizations of subword complexes and multi-associahedra via Gale duality

Abstract

We present complete simplicial fan realizations of any spherical subword complex of type $A_n$ for $n\le 3$. This provides complete simplicial fan realizations of simplicial multi-associahedra ${\Delta }_{2k+4,k}$, whose facets are in correspondence with $k$-triangulations of a convex $(2k+4)$-gon. This solves the first open case of the problem of finding fan realizations where polytopality is not known. The techniques presented in this paper work for all finite Coxeter groups and we hope that they will be useful to construct fans realizing subword complexes in general. In particular, we present fan realizations of two previously unknown cases of subword complexes of type $A_4$, namely the multi-associahedra ${\Delta }_{9,2}$ and ${\Delta }_{11,3}$.

28 pages, 9 figures, 7 tables. v2: Added fan realizations of two multi-associahedra of type A4

References in corpus (3)

• Brick polytopes of spherical subword complexes and generalized associahedra
• Many non-equivalent realizations of the associahedron
• Subword complexes, cluster complexes, and generalized multi-associahedra

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• Braid graphs in simply-laced triangle-free Coxeter systems are partial cubes
• Proof of a conjecture of Bergeron, Ceballos and Labbé