A survey of Computations of Bredon Cohomology

We present an overview of computational methods for Bredon cohomology with a special focus on infinite group

Universal twist in Equivariant K-theory for proper and discrete actions

We define equivariant projective unitary stable bundles as the appropriate twists when defining K-theory as sections of bundles with fibers the space of Fredholm operators over a Hilbert space. We construct universal equivariant projective unitary stable bundles for the orbit types, and we use a specific model for these local universal spaces in order to glue them to obtain a universal equivariant projective unitary stable bundle for discrete and proper actions. We determine the homotopy type of the universal equivariant projective unitary stable bundle, and we show that the isomorphism classes of equivariant projective unitary stable bundles are classified by the third equivariant integral cohomology group. The results contained in this paper extend and generalize results of Atiyah-Segal.Comment: 46 pages. To appear in Proceedings of the London Mathematical Society. This version might differ from the published version, thought its mathematical contents are the sam