Some Work About C~*-Algebra Covariant Extension Theory

Let (A, G, a) be a C*-dynamiacl system where A is a separable nuclear C*-algebra and G is a second countable compact group. Let B be another C*-algebra and Bs denote B (?) K where K is the C*-algebra of all compact operators on a separable Hilbert space. In this thesis, we consider the group ExtG(A,B) of the equivalence classes of covariant extensions (τ,ρ):(A,G,α)�'Q(Bs) and the group ExtG,u(A, B) of the equivalence classes of unital covariant extensions (τ,ρ):(A, G, α)�'Q(Bs) when A has a unit. If G is a trivial group, then ExtG(A,B) is Ext(A,Bs), and ExtG,u(A,B) is Extu(A, Bs).