Representations of nets of C*-algebras over S^1
  In recent times a new kind of representations has been used to describe superselection sectors of the observable net over a curved spacetime, taking into account of the effects of the fundamental group of the spacetime. Using this notion of representation, we prove that any net of C*-algebras over S^1 admits faithful representations, and when the net is covariant under Diff(S^1), it admits representations covariant under any amenable subgroup of Diff(S^1). 
Giuseppe Ruzzi, Ezio Vasselli
math-ph hep-th math.MP math.OA