Constraining decaying dark energy density models with the CMB
  temperature-redshift relation
  We discuss the thermodynamic and dynamical properties of a variable dark
energy model with density scaling as $\rho_x \propto (1+z)^{m}$, z being the
redshift. These models lead to the creation/disruption of matter and radiation,
which affect the cosmic evolution of both matter and radiation components in
the Universe. In particular, we have studied the temperature-redshift relation
of radiation, which has been constrained using a recent collection of cosmic
microwave background (CMB) temperature measurements up to $z \sim 3$. We find
that, within the uncertainties, the model is indistinguishable from a
cosmological constant which does not exchange any particles with other
components. Future observations, in particular measurements of CMB temperature
at large redshift, will allow to give firmer bounds on the effective equation
of state parameter $w_{eff}$ for such types of dark energy models.
