The Cohomology of Real De Concini–Procesi Models of Coxeter Type
1 School of Mathematics and Statistics, University of Sydney, NSW 2006, Australia
2 Department of Mathematics, California Institute of Technology, Pasadena, CA 91125, USA
Correspondence: Correspondence to be sent to: anthonyh{at}maths.usyd.edu.au
We study the rational cohomology groups of the real De Concini–Procesi model corresponding to a finite Coxeter group, generalizing the type-A case of the moduli space of stable genus 0 curves with marked points. We compute the Betti numbers in the exceptional types, and give formulae for them in types B and D. We give a generating-function formula for the characters of the representations of a Coxeter group of type B on the rational cohomology groups of the corresponding real De Concini–Procesi model, and deduce the multiplicities of one-dimensional characters in the representations, and a formula for the Euler character. We also give a moduli space interpretation of this type-B variety, and hence show that the action of the Coxeter group extends to a slightly larger group.
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