Abstract

Recent measurements from the Atacama Cosmology Telescope (ACT), particularly when combined with DESI baryon acoustic oscillation data, have reported a scalar spectral index n<inf>s</inf> slightly higher than that inferred by Planck 2018, suggesting a mild tension with the predictions of standard inflationary attractor models. In this work, we revisit the quantum-corrected Higgs inflation scenario within the framework of a non-minimally coupled scalar field theory. Starting from the one-loop effective action, we incorporate radiative corrections through the anomalous scaling parameter A<inf>I</inf> and derive analytic expressions for the inflationary observables n<inf>s</inf> and r in the Einstein frame. Our analysis demonstrates that quantum corrections naturally shift n<inf>s</inf> toward higher values while keeping the tensor-to-scalar ratio r suppressed. For N=60, the model predicts n<inf>s</inf> ≃ 0.9743 and r≃5.4×10⁻³, in excellent agreement with the latest ACT+DESI (P-ACT-LB) data and fully consistent with the Planck 2018 limit r < 0.036. The derived constraint 4.36×10⁻¹⁰<λ/ξ²<10.77×10⁻¹⁰ confirms the robustness of the quantum-corrected Higgs framework and indicates that near-future CMB polarization experiments such as CORE, AliCPT, LiteBIRD, and CMB-S4 will be able to probe the predicted parameter space with high precision.