Topological Models for Arithmetic

By: William G. Dwyer and Eric M. Friedlander


Abstract. We find explicit models for the etale topological type of certain arithmetic rings A, and in some cases use these models to compute the l-adic topological K-theory of A. Through a comparison map, this gives information about the algebraic K-theory of A. For example, we are able to compute the mod l cohomology of certain "unstable" topological K-theory spaces and verify that it injects into the cohomology of the corresponding unstable algebraic K-theory spaces. This gives an explicit lower bound for H*(GL(n, A); Z=l): In some cases we also find explicit geometric or cohomological reformulations of the Lichtenbaum- Quillen conjectures.
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