On the viability of quintessential inflationary models from   observational data
  Assuming that primordial density fluctuationas are nearly Gaussian, from a frequentist viewpoint, the two-dimensional marginalized joint coincidence contour in the plane $(n_s,r)$ (being $n_s$ the spectral index and $r$ the ratio of tensor to scalar perturbations), without the presence of running is usually used to test the viability of the inflationary models. The models that provide, between $50$ and $60$ e-folds, a curve in that plane, which lies outside the $95.5 \%$ C.L are ruled out. I will basically argue that the this low number of e-folds is unjustified, and that models leading to a theoretical value of the running different from zero must be checked with observational data allowing the running. When both prescriptions are taken into account, dealing in the context of quintessential inflation, i.e. when the potential is a combination of an inflationary with a quintessential one that leads to a deflationary regime, inflationary models such as the quartic or the Higgs potential are allowed. 
Jaume de Haro
gr-qc