Evolution of decaying particles and decay products in various scenarios
  for the future expansion of the universe
  We examine nonrelativistic particles that decay into relativistic products in
big rip, little rip, and pseudo-rip models for the future evolution of the
universe. In contrast to decays that occur in standard $\Lambda$CDM, the
evolution of the ratio $r$ of the energy density of the relativistic decay
products to the energy density of the initially decaying particles can decrease
with time in all of these models. In big rip and little rip models, $r$ always
goes to zero asymptotically, while this ratio evolves to infinity or a constant
in pseudo-rip models.
