Mutated hilltop inflation in light of Planck/ACT observations

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 $r-n_{\mathrm{s}}$ constraints from Planck 2018, BICEP/Keck 2018, and the Atacama Cosmology Telescope (ACT) data, alongside reheating parameters $N_{\mathrm{r}\mathrm{e}}$, $T_{\mathrm{r}\mathrm{e}}$, and ${\omega }_{\mathrm{r}\mathrm{e}}$, and the model independent bound on the radiation dominated (RD) era $N_{\mathrm{r}\mathrm{d}}$. 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 $46\le N\le 56$ (95% CL) and $48.1\le N\le 56$ (68% CL). Moreover, the model parameter $\alpha$ is confined to $0.161\le \alpha \le 0.890$ (95% CL) and $0.217\le \alpha \le 0.815$ (68% CL). Inclusion of the ACT data further tighten the constraints to $54\le N\le 56$ (95% CL) and $0.29\le \alpha \le 0.62$ (95% CL), thereby enhancing the precision and robustness of the model predictions.