Observational constraints on successful model of quintessential Inflation

We study quintessential inflation using a generalized exponential potential V(ϕ)∝  exp (−λ ϕⁿ/M_Plⁿ), 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 ϕ 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 λ is constrained to be, log  λ > −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 ± 0.001 (0.961 ± 0.001) and tiny tensor-to-scalar ratio, r<1.72 × 10⁻² (2.32 × 10⁻²) respectively. Consequently, the upper bound on possible values of the sum of neutrino masses Σ m_ν ≲ 2.5 eV significantly enhances compared to that in the standard ΛCDM model.