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In this paper, we examine the "derived completion" of the
representation ring of a pro–p group Gp^ with
respect to an augmentation ideal. This completion is no longer a
ring: it is a spectrum with the structure of a module spectrum over
the Eilenberg–MacLane spectrum HZ, and can have higher
homotopy information. In order to explain the origin of some of these
higher homotopy classes, we define a deformation representation ring
functor R[–] from groups to ring spectra, and show that the map
R[Gp^]→R[G] becomes an equivalence after
completion when G is finitely generated nilpotent. As an
application, we compute the derived completion of the representation
ring of the simplest nontrivial case, the p–adic Heisenberg group.
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