A dark energy model resulting from a Ricci symmetry revisited

Abstract

Observations of supernovae of type Ia require dark energy (some unknown exotic \emph{`matter'} of negative pressure) to explain their unexpected faintness. Whereas the simplest and most favoured candidate of dark energy, the Einsteinian cosmological constant, is about 120 orders of magnitude smaller than the theoretically predicted value. Motivated by this problem, a number of models of dynamically decaying dark energy have been proposed by considering different phenomenological laws or potentials of the scalar field, which are more or less ad-hoc. However, it is more advisable to consider the symmetry properties of spacetime rather than the ad-hoc assumptions. In this view, we consider a model of Robertson-Walker cosmology emerging from a Ricci symmetry which provides consistently an evolving dark energy. We test the model for the recent supernovae Ia data, as well as, the ultracompact radio sources data compiled by Jackson and Dodgson. The model fits the data very well.