Equivariant cohomology over Lie groupoids and Lie-Rinehart algebras

TL;DR

This paper develops a generalized framework for equivariant cohomology over Lie groupoids and Lie-Rinehart algebras using derived functors, extending classical theories and providing new tools like the cone construction.

Contribution

It introduces a new approach to equivariant cohomology over Lie-Rinehart algebras and Lie groupoids using monads and derived functors, generalizing previous results for Lie groups.

Findings

Equivariant de Rham cohomology over Lie groupoids coincides with stack de Rham cohomology.

The theory reduces to classical equivariant de Rham theory for vertex manifolds.

A cone construction on Lie-Rinehart algebras is introduced as a key tool.

Abstract

Using the language and terminology of relative homological algebra, in particular that of derived functors, we introduce equivariant cohomology over a general Lie-Rinehart algebra and equivariant de Rham cohomology over a locally trivial Lie groupoid in terms of suitably defined monads (also known as triples) and the associated standard constructions. This extends a characterization of equivariant de Rham cohomology in terms of derived functors developed earlier for the special case where the Lie groupoid is an ordinary Lie group, viewed as a Lie groupoid with a single object; in that theory over a Lie group, the ordinary Bott-Dupont-Shulman-Stasheff complex arises as an a posteriori object. We prove that, given a locally trivial Lie groupoid G and a smooth G-manifold f over the space B of objects of G, the resulting G-equivariant de Rham theory of f boils down to the ordinary equivariant de Rham theory of a vertex manifold relative to the corresponding vertex group, for any vertex in the space B of objects of G; this implies that the equivariant de Rham cohomology introduced here coincides with the stack de Rham cohomology of the associated transformation groupoid whence this stack de Rham cohomology can be characterized as a relative derived functor. We introduce a notion of cone on a Lie-Rinehart algebra and in particular that of cone on a Lie algebroid. This cone is an indispensable tool for the description of the requisite monads.