Testing α-attractor quintessential inflation against CMB and low-redshift data

Due to universality and attractor properties, α-attractor quintessential inflation establishes direct relations between inflationary observables such as the scalar tilt n_s and the tensor-to-scalar ratio r, and late-time dark energy equation of state parameters w_0 and w_a. In this work, we examine three different physically motivated regimes, considering complete freedom in the parameter α, models inspired by supergravity where α takes on values up to α=7/3, and Starobinsky inflation (α=1). We investigate the consistency and constraints imposed by Cosmic Microwave Background measurements from the Planck satellite, B-mode polarization data from the BICEP/Keck collaboration, and low-redshift observations. Additionally, we consider small-scale CMB measurements released by the Atacama Cosmology Telescope, which give results approaching the Harrison-Zel'dovich spectrum (n_s ≈ 1). Here α-attractors lead to an improved fit over ΛCDM. For the large-scale CMB measurements, α≳2 models can provide equally good fits as ΛCDM.