Abstract

Recent observations from the Atacama Cosmology Telescope (ACT), especially when combined with DESI baryon acoustic oscillation data, indicate a scalar spectral index ns higher than the value reported by Planck 2018, placing tension on universal inflationary attractor models. Motivated by this discrepancy, we investigate the inflationary predictions of the β-exponential potential, V(ϕ)=V01-λβϕ/Mp1/β considering both minimally and non-minimally coupled realizations. This potential generalizes standard exponential inflation and naturally arises in braneworld scenarios. We derive analytical expressions for the slow-roll parameters and inflationary observables using a perturbative expansion in the non-minimal coupling ξ, and validate these results through numerical calculations. In the minimally coupled case, the model predicts ns≃0.976 and r≃0.035 for N=50 and moderate values of β, remaining compatible with ACT+DESI (P-ACT-LB) constraints at the 1σ level while yielding a spectral tilt larger than the universal attractor prediction. Introducing a small non-minimal coupling significantly improves agreement with observations by suppressing the tensor-to-scalar ratio while preserving the enhanced scalar tilt. For N=60, λ∼0.3-0.5, and β∼O(1-5), the non-minimally coupled model yields ns≃0.974-0.976 and r≲0.03, comfortably consistent with ACT, DESI, and BICEP/Keck bounds. Our results show that the β-exponential potential, especially when implemented with a non-minimal coupling, exhibits good agreement with the latest CMB observations. Our inflationary predictions of the non-minimal model of ns and r confirming the leading-order contributions in ξ are sufficient to capture the essential features of both r and ns in observationally relevant regimes.