Curvaton-assisted hilltop inflation
Abstract
Following the recent Atacama Cosmology Telescope (ACT) results, we consider hilltop inflation where the inflaton is coupled to a curvaton, simultaneously addressing two main challenges faced by conventional hilltop inflation models: the initial-value problem; and their viability for sub-Planckian field values. In standard single-field hilltop inflation, the inflaton must start extremely close to the maximum of the potential, raising concerns about the naturalness of the initial conditions. We demonstrate that the curvaton field not only significantly relaxes the initial-value tuning required for hilltop inflation, but also opens up parameter space through modifying the curvature perturbation power spectrum, reviving the quartic hilltop inflation model in the sub-Planckian regime. We find viable parameter space consistent with the recent cosmological observations.
Cite
@article{arxiv.2512.09079,
title = {Curvaton-assisted hilltop inflation},
author = {Wen-Yuan Ai and Stephen F. King and Xin Wang and Ye-Ling Zhou},
journal= {arXiv preprint arXiv:2512.09079},
year = {2026}
}
Comments
15 pages, 4 figures, 1 table. Substantial changes including revised formulas for primordial observables and additional discussions and references