Mutated hilltop inflation in light of Planck/ACT observations

We investigate the observational viability of a single field inflationary model driven by a mutated hilltop potential. To rigorously constrain the parameter space of the model, we perform a joint analysis utilizing the latest cosmic microwave background measurements, including Planck 2018, BICEP/Keck 2018, and Atacama Cosmology Telescope (ACT) data. We combine these cosmic microwave background constraints with post inflationary physical bounds derived from the reheating epoch. Specifically, we incorporate the duration [Formula: see text], the temperature [Formula: see text], and the equation of state [Formula: see text] alongside the model independent duration of the radiation dominated era [Formula: see text]. Furthermore, we evaluate the predicted relic gravitational wave spectrum against the sensitivity domains of upcoming gravitational wave interferometers. Our combined analysis reveals that for the Planck+BK18 dataset, the inflationary duration is strictly confined to [Formula: see text], while the potential parameter is bounded to [Formula: see text] at the 95% confidence level. Remarkably, the inclusion of ACT data significantly tightens these constraints, narrowing the viable parameter space to [Formula: see text] and [Formula: see text] (95% CL). We conclude that the mutated hilltop model exhibits high precision and robust compatibility with current cosmological data, and crucially, predicts a relic GW background that falls within the detection capabilities of future observatories.