Observational constraints on successful model of quintessential
  Inflation
  We study quintessential inflation using a generalized exponential potential
$V(\phi)\propto exp(-\lambda \phi^n/Mpl^n), n>1$, the model admits slow-roll
inflation at early times and leads to close-to-scaling behaviour in the post
inflationary era with an exit to dark energy at late times. We present detailed
investigations of the inflationary stage in the light of the Planck 2015
results, study post-inflationary dynamics and analytically confirm the
existence of an approximately scaling solution. Additionally, assuming that
standard massive neutrinos are non-minimally coupled, makes the field $\phi$
dominant once again at late times giving rise to present accelerated expansion
of the Universe. We derive observational constraints on the field and
time-dependent neutrino masses. In particular, for $n=6 (8)$, the parameter
$\lambda$ is constrained to be,$\log \lambda > -7.29 (-11.7)$; the model
produces the spectral index of the power spectrum of primordial scalar (matter
density) perturbations as $ n_s = 0.959 \pm 0.001 (0.961 \pm 0.001)$ and tiny
tensor-to-scalar ratio, $r<1.72 \times 10^{-2} (2.32 \times 10^{-2})$
respectively. Consequently, the upper bound on possible values of the sum of
neutrino masses $\Sigma m_{\nu} \lesssim 2.5$ eV significantly enhances
compared to that in the standard $\Lambda$CDM model.
