  FLRW equations are analyzed in a universe with a cosmic scalar background
that is spatially uniform but time-varying. Some solvable potentials to the
combined dynamics in such a universe are presented, that are consistent with
the scalar dynamics as a consequence of energy momentum conservation. Certain
potentials are found to provide very good fits to type Ia supernovae data, with
the kinetic and potential energies of the scalar providing the source for dark
matter and dark energy. The scalar rolls down the potential as the universe
expands with the potential playing the role of a time-varying cosmological
constant, modeling a scenario recently discussed in the literature.
