A divergence-free parametrization for dynamical dark energy
  We introduce a new parametrization for the dark energy, led by the same idea
to the linear expansion of the equation of state in scale factor $a$ and in
redshift $z$, which diverges neither in the past nor future and contains the
same number of degrees of freedom with the former two. We present constraints
of the cosmological parameters using the most updated baryon acoustic
oscillation (BAO) measurements along with cosmic microwave background (CMB)
data and a recent reanalysis of Type Ia supernova (SN) data. This new
parametrization allowed us to carry out successive observational analyses by
decreasing its degrees of freedom systematically until ending up with a
dynamical dark energy model that has the same number of parameters with
$\Lambda$CDM. We found that the dark energy source with a dynamical equation of
state parameter equal $-2/3$ at the early universe and $-1$ today fits the data
slightly better than $\Lambda$.
