Phenomenological model for inflationary quintessence

We present a phenomenologically motivated model which is able to give rise both to an inflationary epoch and to the present day cosmic acceleration. We introduce an approach where the energy density depends on the scale factor a in such a way that a smooth transition from the inflation to the matter dominated era and then to the current accelerated expansion is achieved. We use the dimensionless coordinate distance y(z) to the gold type Ia supernovae data set and to a sample comprising 20 radio galaxies, the shift parameter R, and the acoustic peak parameter A to test whether the model is in agreement with observations and to constrain its main parameters. As an independent cross-check, we also compare model predictions with the look-back time to galaxy clusters and the age of the universe. Although phenomenologically inspired, the model may be theoretically motivated either resorting to a scenario with scalar and phantom fields (eventually interacting) or as an effective description arising from higher order gravity theories.