Amenability properties of the central fourier algebra of a compact group

Journal article, 2016

We let the central Fourier algebra, ZA(G), be the subalgebra of functions u in the Fourier algebra A(G) of a compact group, for which u(xyx-1) = u(y) for all x, y in G. We show that this algebra admits bounded point derivations whenever G contains a non-Abelian closed connected subgroup. Conversely when G is virtually Abelian, then ZA(G) is amenable. Furthermore, for virtually Abelian G, we establish which closed ideals admit bounded approximate identities. We also show that ZA(G) is weakly amenable, in fact hyper-Tauberian, exactly when G admits no non-Abelian connected subgroup. We also study the amenability constant of ZA(G) for finite G and exhibit totally disconnected groups G for which ZA(G) is non-amenable. In passing, we establish some properties related to spectral synthesis of subsets of the spectrum of ZA(G).