Published online by Cambridge University Press: 24 October 2008
Following a program of Reiter, sets of synthesis in Banach algebras with certain Ditkin conditions are discussed. It is shown that the Ditkin Shilov lemma is in a general context best possible. Various methods for the construction of algebras are discussed. These are applied to show that very strong homogeneity conditions are needed to ensure that star sets are of synthesis for regular Ditkin algebras with Rn as carrier space.