给出了纯无限单的C^*-代数A通过κ的扩张代数E的K-理论的一种刻划。证明了Ko(E)等于E中所有无限投影的Murry—von Neumann等价类所成的交换群,K1(E)等于E中酉元的同伦等价类所成的交换群。作为一个应用,最后给出了A中酉元可提升的等价条件,其中咒为可分无限维Hilbert空间上紧算子全体所成的C^*-代数。
This paper computes K-theory for C^*-algebra E which is the extension of purely infinite simple C^*-algebras A by κ, the C^*-algebra of all compact oprators on separable infinite dimensional Hilbert space. The authors prove that Ko(E) is the group of all Merryvon Neumann equivalent classes of all infinite projections in E and Ka(E) is the group of all homotopy equivalent classes of unitaries in E. As an application, some equivalent conditions of lifting unitaries of A are given.