A characterization of the closed unital ideals of the Fourier-Stieltjes algebra B(G) of a locally compact amenable group G

Let G be a locally compact amenable group, B(G) its Fourier-Stieltjes algebra and I be a closed ideal of it. In this paper we prove the following result: The ideal I has a unit element iff it is principal. This is the noncommutative version of the Glicksberg-Host-Parreau Theorem. The paper also contains an abstract version of this theorem.