NEW LIMITS TO THE INFRARED BACKGROUND - BOUNDS ON RADIATIVE NEUTRINO DECAY AND ON CONTRIBUTIONS OF VERY MASSIVE OBJECTS TO THE DARK-MATTER PROBLEM

From considering the effect of gamma-gamma interactions on recently ob served TeV gamma ray spectra, improved limits are set to the density o f extragalactic infrared photons which are robust and essentially mode l independent. The resulting limits are more than an order of magnitud e more restrictive than direct observations in the 0.025-0.3 eV regime . These limits are used to improve constraints on radiative neutrino d ecay in the mass range above 0.05 eV and to rule out very massive obje cts as providing the dark matter needed to explain galaxy rotation cur ves. Lower bounds on the maximum distance which TeV gamma rays may pro be are also derived.