Summary of the ECFA Linear Collider Working Group on Beamstrahlung and Photon-Photon Interactions

This paper presents a concise summary of the developments achieved in the context of the ''Photons'' Working Group of the 1991 ECFA Workshop on Physics with Linear Colliders. After reviewing, in Section 2, the current knowledge on the beam-beam interaction and its main physics implications, they calculate in Section 3 effective photon and electron luminosity spectra. Section 4 discusses background issues associated with photon-photon processes. Finally, they briefly survey, in Section 5, recent updates on the principle issues and the physics potential of the so-called ''Compton Collider''