We prove a Paley–Wiener theorem for the spectral projection of symmetric graphs
and, as a corollary, derive a Paley–Wiener theorem for the Helgason–Fourier
transform. The proof is based on contour integration arguments similar to those used
to prove the Paley–Wiener theorem for Euclidean spaces and symmetric
spaces.
Keywords
spectral projection, symmetric graph, Paley–Wiener theorem,
generalized spherical function