Let $G$ be a metrizable compact group, $A$ a separable ${{\text{C}}^{*}}$-algebra, and $\alpha :G\,\to \,\text{Aut}\left( A \right)$ a strongly continuous action. Provided that $\alpha $ satisfies the continuous Rokhlin property, we show that the property of satisfying the $\text{UCT}$ in $E$-theory passes from $A$ to the crossed product ${{\text{C}}^{*}}$-algebra $\mathcal{A}{{\rtimes }_{\alpha }}\,G$ and the fixed point algebra ${{A}^{\alpha }}$. This extends a similar result by Gardella for $KK$-theory in the case of unital ${{\text{C}}^{*}}$-algebras but with a shorter and less technical proof. For circle actions on separable unital ${{\text{C}}^{*}}$-algebras with the continuous Rokhlin property, we establish a connection between the $E$-theory equivalence class of $A$ and that of its fixed point algebra ${{A}^{\alpha }}$.

A. Bonkat obtained a universal coefficient theorem in the setting of Kirchberg's ideal-related $KK$-theory in the fundamental case of a ${{C}^{*}}$-algebra with one specified ideal. The universal coefficient sequence was shown to split, unnaturally, under certain conditions. Employing certain $K$-theoretical information derivable from the given operator algebras using a method introduced here, we shall demonstrate that Bonkat's $\text{UCT}$ does not split in general. Related methods lead to information on the complexity of the $K$-theory which must be used to classify $*$-isomorphisms for purely infinite ${{C}^{*}}$-algebras with one non-trivial ideal.

We define and compare two bivariant generalizations of the topological K - group Ktop(G). We consider the Baum-Connes conjecture in this context and study its relation to the usual Baum-Connes conjecture.