Mutated hilltop inflation in light of Planck/ACT observations

TL;DR

This paper investigates a mutated hilltop inflation model constrained by recent CMB and GW observations, refining parameter bounds and analyzing the relic gravitational wave spectrum for future detector sensitivity.

Contribution

It introduces a detailed analysis of mutated hilltop inflation constrained by latest observational data, providing tighter bounds on model parameters and relic GW spectrum predictions.

Findings

Inflationary duration confined to 46-56 e-folds with Planck+BK18 data.

Model parameter alpha constrained to 0.161-0.890 (95% CL).

Constraints tightened with ACT data to 54-56 e-folds and alpha 0.29-0.62.

Abstract

Here, a single field inflationary model driven by a mutated hilltop potential, a subclass of the hilltop models of inflation, is investigated. To constrain the parameter space, we employ the latest $r-n_{\rm s}$ constraints from Planck 2018, BICEP/Keck 2018, and the Atacama Cosmology Telescope (ACT) data, alongside reheating parameters $N_{\rm{re}}$, $T_{\rm{re}}$, and $\omega_{\rm{re}}$, and the model independent bound on the radiation dominated (RD) era $N_{\rm{rd}}$. Furthermore, the relic gravitational wave (GW) spectrum within the sensitivity domains of future GW detectors are analyzed. By combining CMB, reheating, RD era, and GW constraints, we find for the Planck+BK18 data that the inflationary duration is confined to $46 \leq N \leq 56$ (95\% CL) and $48.1 \leq N \leq 56$ (68\% CL). Moreover, the model parameter $\alpha$ is confined to $0.161 \leq \alpha \leq 0.890$ (95\% CL) and $0.217 \leq \alpha \leq 0.815$ (68\% CL). Inclusion of the ACT data further tighten the constraints to $54 \leq N \leq 56$ (95\% CL) and $0.29 \leq \alpha \leq 0.62$ (95\% CL), thereby enhancing the precision and robustness of the model predictions.