Quintessence From a Decaying Dark Matter

It is a known fact that a quintessence model with $w_q < -1$ fits the publicly available Super Nova (SN) type Ia data better than a model with cosmological constant or $w_q > -1$. Two types of models have this property: Scalar fields with unconventional kinetic term and models with cosmological constant and a slowly decaying Cold Dark Matter (CDM). In this work we investigate the possibility of replacing the cosmological constant in the latter models with gradual condensation of a scalar field produced during the decay of the CDM and present some preliminary results. The advantage of this class of models to the ordinary quintessence is that the evolution of the dark energy and CDM are correlated and cosmological coincidence problem is solved or at least reduced to the fine tuning of the coupling between decaying CDM and quintessence field i.e the Hierarchy problem. Here we show that for part of the parameter space these models are consistent with present estimation of cosmological parameters.