Using a Phenomenological Model to Test the Coincidence Problem of Dark Energy

By assuming a phenomenological form for the ratio of the DE and DM densities X ₌ a^ (Dalal et al. 2001), we discuss the cosmic coincidence problem in light of current observational data. is a key parameter to denote the severity of the coincidence problem. In this scenario, =3 and =0 correspond to CDM and the self-similar solution without coincidence problem, respectively. Hence, any solution with a scaling parameter 0 0. 73, within the framework of this model, we can conclude that the interaction between DE and DM is necessary.