Abstract
We show that the Simion type B associahedron is combinatorially equivalent to a pulling triangulation of the type A root polytope known as the Legendre polytope. Furthermore, we show that every pulling triangulation of the boundary of the Legendre polytope yields a flag complex. Our triangulation refines a decomposition of the boundary of the Legendre polytope given by Cho. Finally, we extend Cho’s cyclic group action to the triangulation in such a way that it corresponds to rotating centrally symmetric triangulations of a regular \((2n+2)\)-gon.
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Acknowledgements
The authors thank the Princeton University Mathematics Department where this research was initiated. The first author was partially funded by the National Security Agency Grant H98230-13-1-028. This work was partially supported by grants from the Simons Foundation (# 429370 to Richard Ehrenborg, # 245153 and # 514648 to Gábor Hetyei, # 206001 and # 422467 to Margaret Readdy). The authors also thank the three anonymous referees for their comments.
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Ehrenborg, R., Hetyei, G. & Readdy, M. Simion’s Type B Associahedron is a Pulling Triangulation of the Legendre Polytope. Discrete Comput Geom 60, 98–114 (2018). https://doi.org/10.1007/s00454-018-9973-4
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DOI: https://doi.org/10.1007/s00454-018-9973-4
Keywords
- Bott–Taubes polytope
- Compressed polytopes
- Cyclohedron
- Flag complex
- Stasheff polytope
- Type A root polytope