An index theorem for families invariant with respect to a bundle of Lie groups

Abstract

We define the equivariant family index of a family of elliptic operators invariant with respect to the free action of a bundle \GR of Lie groups. If the fibers of \GR \to B are simply-connected solvable, we then compute the Chern character of the (equivariant family) index, the result being given by an Atiyah-Singer type formula. We also study traces on the corresponding algebras of pseudodifferential operators and obtain a local index formula for such families of invariant operators, using the Fedosov product. For topologically non-trivial bundles we have to use methods of non-commutative geometry. We discuss then as an application the construction of ``higher-eta invariants,'' which are morphisms K_n(\PsS {\infty}Y) \to \CC. The algebras of invariant pseudodifferential operators that we study, \Psm {\infty}Y and \PsS {\infty}Y, are generalizations of ``parameter dependent'' algebras of pseudodifferential operators (with parameter in \RR^q), so our results provide also an index theorem for elliptic, parameter dependent pseudodifferential operators.Comment: AMS-Latex, 39 pages, references, corrections, and new results adde