Genesis-Starobinsky inflation can explain the ACT data
Year: 2026
Type: article
Abstract: We propose a novel non-singular cosmological scenario within the framework of Horndeski gravity, consisting of three successive stages: (i) a Genesis phase, in which the Universe slowly expands from an asymptotically flat spacetime; (ii) a brief transition stage and (iii) a Starobinsky inflationary phase. This construction is fully consistent within a viable parameter space: it remains weakly coupled, free from ghost and gradient instabilities, with luminal tensor and subluminal scalar perturbations throughout the entire evolution. Importantly, the Genesis phase induces characteristic corrections to the Starobinsky potential, which cannot be captured by simple ∑ i c i R i -type modifications. These corrections robustly enhance the scalar spectral index, thereby improving the agreement of Starobinsky inflation with recent CMB measurements, in particular the data from the Atacama Cosmology Telescope (ACT).
Authors: Han Gil Choi, Pavel Petrov, Seong Chan Park
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,290
OpenAlex ID: W4414760378