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Séminaire Algèbre ICJ

# Reflection length in affine Coxeter groups

## by Petra Schwer (Karlsruhe Institute of Technology)

jeudi 26 avril 2018 de au (Europe/Paris)
at bât. Braconnier ( 112 )
ICJ, UCBL - La Doua
 Description Affine Coxeter groups have a natural presentation as reflection groups on some affine space. Hence the set R of all its reflections, that is all conjugates of its standard generators, is a natural (infinite) set of generators. Computing the reflection length of an element in an affine Coxeter group means that one wants to determine the length of a minimal presentation of this element with respect to R. In joint work with Joel Brewster Lewis, Jon McCammond and T. Kyle Petersen we were able to provide a simple formula that computes the reflection length of any element in any affine Coxeter group. In this talk I would like to explain this formula, give its simple uniform proof and allude to the geometric intuition behind it.