A generalization to the non-separable case of Takesaki's duality theorem forC *-algebras

Takesaki [5] poses the question of how much information about aC^*-algebraA is contained in its representation theory. He gives it a precise meaning in the following setting: One can furnish the set Rep (A:H) of all representations ofA in a suitable Hilbert spaceH with a topology, with an action of the unitary groupG ofB(H) on it, and with an addition. The setA^F of operator fields Rep (A:H)B(H) commuting with the action ofG and addition, called the admissible operator fields, turn out to form aW^*-algebra isomorphic to the bidual ofA with Arens multiplication or with the universal enveloping von Neumann algebra ofA. Takesaki shows in the separable case thatA can be identified inA^F as the set of continuous admissible operator fields, and leaves the same question open for arbitraryC^*-algebras. Changing the structures on Rep(A:H) slightly, it is shown here that this result obtains in the general case as well. The proof proceeds along the lines set up in [5] but makes no use of the representation theory of NGCR algebras.