The inverse backscattering problem in three dimensions

This article is a study of the mapping from a potentialq(x) onR3 to the backscattering amplitude associated with the Hamiltonian −Δ+q(x). The backscattering amplitude is the restriction of the scattering amplitudea(θ, ω, k), (θ, ω, k)εS2×S2×ℝ+, toa(θ,−θ, k). We show that in suitable (complex) Banach spaces the map fromq(x) toa(x/|x|, −x/|x|, |x|) is usually a local diffeomorphism. Hence in contrast to the overdetermined problem of recoveringq from the full scattering amplitude the inverse backscattering problem is well posed.