English

Homomorphisms from AH-algebras

Operator Algebras 2015-08-06 v6

Abstract

Let CC be a general unital AH-algebra and let AA be a unital simple CC^*-algebra with tracial rank at most one. Suppose that ϕ,ψ:CA\phi, \psi: C\to A are two unital monomorphisms. We show that ϕ\phi and ψ\psi are approximately unitarily equivalent if and only if \beq[\phi]&=&[\psi] {\rm in} KL(C,A), \phi_{\sharp}&=&\psi_{\sharp}\tand \phi^{\dag}&=&\psi^{\dag}, \eneq where ϕ\phi_{\sharp} and ψ\psi_{\sharp} are continuous affine maps from tracial state space T(A)T(A) of AA to faithful tracial state space Tf(C)T_{\rm f}(C) of CC induced by ϕ\phi and ψ,\psi, respectively, and ϕ\phi^{\ddag} and ψ\psi^{\ddag} are induced homomorphisms from K1(C)K_1(C) into \Aff(T(A))/ρA(K0(A))ˉ,\Aff(T(A))/\bar{\rho_A(K_0(A))}, where \Aff(T(A))\Aff(T(A)) is the space of all real affine continuous functions on T(A)T(A) and ρA(K0(A))ˉ\bar{\rho_A(K_0(A))} is the closure of the image of K0(A)K_0(A) in the affine space \Aff(T(A)).\Aff(T(A)). In particular, the above holds for C=C(X),C=C(X), the algebra of continuous functions on a compact metric space. An approximate version of this is also obtained. We also show that, given a triple of compatible elements κKLe(C,A)++,\kappa\in KL_e(C,A)^{++}, an affine map γ:T(C)Tf(C)\gamma: T(C)\to T_{\rm f}(C) and a \hm \af:K1(C)\Aff(T(A))/ρA(K0(A))ˉ,\af: K_1(C)\to \Aff(T(A))/\bar{\rho_A(K_0(A))}, there exists a unital monomorphism ϕ:CA\phi: C\to A such that [h]=κ,[h]=\kappa, h=γh_{\sharp}=\gamma and ϕ=\af.\phi^{\dag}=\af.

Keywords

Cite

@article{arxiv.1102.4631,
  title  = {Homomorphisms from AH-algebras},
  author = {Huaxin Lin},
  journal= {arXiv preprint arXiv:1102.4631},
  year   = {2015}
}
R2 v1 2026-06-21T17:30:18.525Z