Problems and stoppers for gamma-gamma, gamma-mu, mu-p colliders using   very high energy muons
  It is well known that at linear e^+e^-(e^-e^-) colliders using laser backscattering one can obtain colliding gamma-gamma, gamma-electron beams with energy and luminosity comparable to those in e^+e^- collisions. In this paper, it is explained why this can not be done at high energy muon colliders. Due to several physics reasons the gamma-gamma luminosity is suppressed here by a factor of 10^{14} ! Another option -- gamma's from a linear collider and muons from a muon collider -- is also discussed (and has no sense either). Of course, one can study gamma^*-muon and gamma^*-gamma^* interactions at muon colliders in collisions with virtual photons as it is done now at e^+e^- storage rings. Muon-proton colliders are attractive only if the proton beam is cooled and has the same parameters as the muon beam, in which case   L_{\mu p} \sim L_{\mu\mu}. 
Valery Telnov (Budker Institute of Nuclear Physics)