Late decaycing dark matter as dark energy

We discuss a cosmology in which cold dark-matter begins to decay into relativistic particles at a recent epoch (z < 1). We show that the large entropy production and associated bulk viscosity from such decays leads to a recently accelerating cosmology consistent with observations. We investigate the effects of decaying cold dark matter in a Λ = 0, flat, initially matter dominated cosmology. We show that this model satisfies the cosmological constraint from Type Ia supernovae at high redshift. Possible additional observational tests of this new cosmological paradigm are suggested.