An Operator Space duality theorem for the Fourier-Stieltjes algebra of a locally compact groupoid

Abstract

It is a well-known result of Eymard that the Fourier-Stieltjes algebra of a locally compact group $G$ can be identified with the dual of the group $\cs$ $C^{*}(G)$. A corresponding result for a locally compact groupoid $G$ has been investigated by Renault, Ramsay and Walter. We show that the Fourier-Stieltjes algebra $B_{\mu}(G)$ of $G$ (with respect to a quasi-invariant measure $\mu$ on the unit space $X$ of $G$) can be characterized in operator space terms as the dual of the Haagerup tensor product $\ov{L^{2}(X,\mu)}^{r}\otimes_{hA}C^{*}(G,\mu)\otimes_{h A}L^2(X,\mu)^c$ and as the space of completely bounded bimodule maps $CB_{A}(C^{*}(G,\mu),B(L^2(X,\mu)))$, where $A=C_{0}(X)$ and $C^{*}(G,\mu)$ is the groupoid $\cs$ obtained from those $G$-representations associated with $\mu$. A similar but different result has been given by Renault, but our proof is along different lines, and full details are given. Examples illustrating the result are discussed.