  As the 2015 results of Plancks mission have recently been made available, it
is interesting to check the evolution of the scale factor and of the Hubble
parameter in the light of these results. Two models in line with Einsteins
field equations and with the hot big bang scenario for a flat Universe are used
to allow a comparison : (1) the classical one using density parameters for
matter content (baryonic and dark matter) and dark energy ; (2) an alternative
model, already used in the past, and assuming the Hubble parameter to contain a
term constant in time. Both models are coherent with each other except for some
discrepancy about the density, which can be ascribed to the different
hypotheses made. This opens a way for further interpretation of the origin of
dark energy.
