Cambrian fan and cluster poset correspondence conjecture

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Let WW be a finite crystallographic Coxeter group with root system Φ\Phi, simple roots αi\alpha_i, fundamental weights ωi\omega_i, and a bipartition G=I+∪I−G=I_+\cup I_- of its Coxeter diagram. Set ε(i)=+1\varepsilon(i)=+1 for i∈I+i\in I_+ and ε(i)=−1\varepsilon(i)=-1 for i∈I−i\in I_-. The cluster fan is the fan whose maximal cones are generated by the clusters of roots, and the orientation I+⟶I−I_+\longrightarrow I_- directs every edge from I+I_+ to I−I_-. Cambrian cluster correspondence conjecture. The linear map αi↦ε(i)ωi\alpha_i\mapsto\varepsilon(i)\omega_i maps the cluster fan for WW isomorphically to the Cambrian fan for the orientation I+⟶I−I_+\longrightarrow I_-, and the Cambrian lattice for this orientation is the cluster poset. This identifies the geometric and order-theoretic Cambrian objects with the cluster fan and cluster poset. The statement is solved: the paper proves it in the relevant development, including the type-AA and type-BB cases discussed there.

References

Primary source

Nathan Reading, “Cambrian Lattices”, arXiv:math/0402086 (2005).

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