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Permutahedra and generalized associahedra. (English) Zbl 1233.20035
Suppose that $$(W,S)$$ is a finite Coxeter system and $$c\in W$$ is a Coxeter element (a product of the simple reflections in some order). N. Reading [Adv. Math. 205, No. 2, 313-353 (2006; Zbl 1106.20033)] has associated to this data the corresponding $$c$$-Cambrian fan $$\mathcal F_c$$ and conjectured that every such fan is the normal fan of a polytope.
The main result of this article is a proof of this conjecture, via the construction of a $$c$$-generalized associahedron. Note that Cambrian fans are known to be linearly isomorphic to $$\mathbf g$$-vector fans of finite type cluster algebras with respect to an acyclic initial seed. This was proved by N. Reading and D. E. Speyer [in J. Eur. Math. Soc. 11, No. 2, 407-447 (2009; Zbl 1213.20038)] modulo a conjecture of S. Fomin and A. Zelevinsky [Compos. Math. 143, No. 1, 112-164 (2007; Zbl 1127.16023)] which was later proved by S.-W. Yang and A. Zelevinsky [Transform. Groups 13, No. 3-4, 855-895 (2008; Zbl 1177.16010)].

##### MSC:
 20F55 Reflection and Coxeter groups (group-theoretic aspects) 52B11 $$n$$-dimensional polytopes 05E15 Combinatorial aspects of groups and algebras (MSC2010) 06A07 Combinatorics of partially ordered sets
##### Citations:
Zbl 1106.20033; Zbl 1213.20038; Zbl 1127.16023; Zbl 1177.16010
CHEVIE; GAP
Full Text:
##### References:
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