The Isomorphism Conjecture in algebraic K-theory

Let Γ\Gamma be a group. The group K0(CΓ)K_0(\mathbb C\Gamma) is the Grothendieck group of finitely generated projective CΓ\mathbb C\Gamma-modules, and FinΓ\mathcal F in \Gamma denotes the family of finite subgroups of Γ\Gamma. The Isomorphism Conjecture in algebraic KK-theory predicts that K0(CΓ)K_0(\mathbb C\Gamma) should be computable from the KK-theory of the complex group rings of finite subgroups of Γ\Gamma.

Isomorphism Conjecture in algebraic KK-theory. The map from the colimit over finite subgroups

colimHFinΓK0(CH)K0(CΓ)\operatorname{colim}_{H\in\mathcal F in \Gamma}K_0(\mathbb C H)\longrightarrow K_0(\mathbb C\Gamma)

should be an isomorphism. In particular, for a torsionfree group Γ\Gamma,

K0(CΓ)Z.K_0(\mathbb C\Gamma)\cong\mathbb Z.

This is a special case of the algebraic KK-theory isomorphism conjecture discussed in the paper. The source gives no resolution status for this formulation.

Sources & referencesView supporting material

Primary source

Holger Reich, “L^2-Betti numbers, isomorphism conjectures and noncommutative localization”, arXiv:math/0303097 (2003).

Additional references

2 papers in this index state this conjecture (2001–2003). The statement above is taken from the most recent of them; the others are arXiv:math/0108139.

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