We show that existing decay results for scalar fields on the Schwarzschild
metric are sufficient to obtain a conformal scattering theory. Then we
re-interpret this as an analytic scattering theory defined in terms of wave
operators, with an explicit comparison dynamics associated with the principal
null geodesic congruences. The case of the Kerr metric is also discussed.Comment: 36 pages, 6 figures. From the first version, recent references have
been added and the discussion has been modified to take the new references
into account. To appear in Annales de l'Institut Fourie
