COSMOLOGICAL SIGNATURES OF DECAYING DARK-MATTER

The decaying dark matter (DDM) scenario is a viable way of ionizing th e Universe at high redshifts. We examine the constraints on this scena rio due to the diffuse ultraviolet flux and Gunn-Peterson tests. The l atter require the decaying particle's lifetime to be less than approxi mately 10(23) S. Observations of the diffuse UV flux along with a cons ervative estimate of its Galactic component require the DDM particle t o have mass greater than 28.5 eV. With larger estimates of the Galacti c contribution to the UV flux, the limit becomes m > 34.5 Ev. We also point out a distinctive signature of DDM: a sharp drop in the infrared part of the spectrum.