A Refined Count of Coxeter Element Reflection Factorizations

Elise delMas, Thomas Hameister, Victor Reiner


For well-generated complex reflection groups, Chapuy and Stump gave a simple product for a generating function counting reflection factorizations of a Coxeter element by their length. This is refined here to record the number

of reflections used from each orbit of hyperplanes. The proof is case-by-case via the classification of well-generated groups. It implies a new expression for the Coxeter number, expressed via data coming from a hyperplane orbit; a case-free proof of this due to J. Michel is included.


Reflection group; Coxeter element; Factorization; Well-generated

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