Eta-invariants and Molien series for unimodular group

Abstract

We look at the singularity Cn/[Gamma], for [Gamma] finite subgroup of SU(n), from two perspectives. From a geometrical point of view, Cn/[Gamma] is an orbifold with boundary S2n-1/[Gamma]. We define and compute the corresponding orbifold [eta]-invariant. From an algebraic point of view, we look at the algebraic variety Cn/[Gamma] and we analyze the associated Molien series. The main result is formula which relates the two notions: [eta]-invariant and Molien series. Along the way computations of the spectrum of the Dirac operator on the sphere are performed.