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Excision for deformation K-theory of free products

Daniel A. Ramras
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Abstract

Associated to a discrete group $G$, one has the topological category of finite dimensional (unitary) $G$-representations and (unitary) isomorphisms. Block sums provide this category with a permutative structure, and the associated $K$-theory spectrum is Carlsson's deformation $K$-theory of G. The goal of this paper is to examine the behavior of this functor on free products. Our main theorem shows the square of spectra associated to $G*H$ (considered as an amalgamated product over the trivial group) is homotopy cartesian. The proof uses a general result regarding group completions of homotopy commutative topological monoids, which may be of some independent interest.

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Daniel A. Ramras. 2018-05-08. Excision for deformation K-theory of free products. https://doi.org/10.2140/agt.2007.7.2239

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