Constraining the quintessential α-attractor inflation through dynamical horizon exit method

Abstract

In the present paper, we perform a sub-Planckian quantum mode analysis of linear cosmological perturbation in the inflaton field over a classical quasi de-Siter metric background by dynamical horizon exit (DHE) method. In this way, we probe the inflationary regime of a quintessential α-attractor model by analysing the COBE/Planck normalized power spectra, spectral indices, tensor to scalar ratio, number of e-folds, running of the spectral index and inflationary Hubble parameter in k-space. We compare our results with ordinary α-attractor E and T models and with that of Planck-2018 results. Our estimated values of ns and r lie within 68% CL with respect to Planck data for k=0.001–0.009 Mpc−1 for all values of α. The α values, obtained in our calculations satisfy various post inflationary constraints regarding preheating and reheating, reported in current literature. We observe that quintessence sets an upper bound of α=4.3 and thereby restricts the model from becoming of the power law type, making it more efficacious than ordinary α-attractors in explaining both inflation and dark energy. A striking observation in our analyses is that, unlike in our previous study, we find a continuous values of α within ≤α≤4.3 for the specified k range. At the end, we have shown that the model parameters constrained in this work give a very small vacuum density ∼10−117–10−115MP4 which is an essential criterion for current and future dark energy observations of the universe.