抄録
As an aid in understanding sets of synthesis for the Fourier algebra A(G) of a locally compact abelian group G, the difference spectrum Δ(E) for a closed set E in G is studied. Numerous relations involving difference spectra of unions, intersections and cartesian products are obtained and their implications on unions, intersections and cartesian products of sets of spectral synthesis are deduces. The set Λ(E) of locally nonsynthesizable points of E is introduces and its relation with Δ(E) is discussed. The concept of n-difference spectrum is introduced and is used to study weak spectral synthesis. Local methods are employed throughout.
