Published online by Cambridge University Press: 20 November 2018
We prove that pre-classifiable (see 3.1) simple nuclear tracially $\text{AF}\,\,{{C}^{*}}$-algebras
$\left( \text{TAF} \right)$ are classified by their
$K$-theory. As a consequence all simple, locally
$\text{AH}$ and
$\text{TAF}\,\,\,{{C}^{*}}$-algebras are in fact
$\text{AH}$ algebras (it is known that there are locally
$\text{AH}$ algebras that are not
$\text{AH}$). We also prove the following Rationalization Theorem. Let
$A$ and
$B$ be two unital separable nuclear simple
$\text{TAF}\,\,\,{{C}^{*}}$-algebras with unique normalized traces satisfying the Universal Coefficient Theorem. If
$A$ and
$B$ have the same (ordered and scaled)
$K$-theory and
${{K}_{0}}{{\left( A \right)}_{+}}$ is locally finitely generated, then
$A\,\otimes \,Q\,\cong \,B\,\otimes \,Q$, where
$Q$ is the
$\text{UHF}$-algebra with the rational
${{K}_{0}}$. Classification results (with restriction on
${{K}_{0}}$ - theory) for the above
${{C}^{*}}$-algebras are also obtained. For example, we show that, if
$A$ and
$B$ are unital nuclear separable simple
$\text{TAF}\,\,\,{{C}^{*}}$-algebras with the unique normalized trace satisfying the
$\text{UCT}$ and with
${{K}_{1}}\left( A \right)\,=\,{{K}_{1}}\left( B \right)$, and
$A$ and
$B$ have the same rational (scaled ordered)
${{K}_{0}}$, then
$A\,\cong \,B$. Similar results are also obtained for some cases in which
${{K}_{0}}$ is non-divisible such as
${{K}_{0}}\left( A \right)\,=\,\mathbf{Z}\left[ 1/2 \right]$.