Quantum-corrected ^4 inflation in light of ACT observations

Abstract Recent measurements from the Atacama Cosmology Telescope (ACT), combined with Planck and DESI data, suggest a scalar spectral index nₛ n s higher than the Planck 2018 baseline, thereby placing conventional attractor-type inflationary models such as Starobinsky R² R 2 and Higgs inflation under increasing tension at the 2 ≳ 2 σ level. In this work, we examine quantum-corrected ⁴ ϕ 4 inflation with a non-minimal coupling to gravity. Introducing an anomalous scaling parameter γ to capture quantum corrections to the effective potential, we derive analytic expressions for the inflationary observables nₛ n s and r. Confronting these predictions with ACT, Planck, and BAO+lensing constraints, we demonstrate that modest values of γ can raise nₛ n s into the ACT-preferred range while maintaining a strongly suppressed tensor-to-scalar ratio. For instance, with N=60 N = 60 and 0. 006 γ ≃ 0. 006, the model predicts nₛ 0. 974 n s ≃ 0. 974 and r 0. 007 r ≃ 0. 007, in excellent agreement with current bounds. We further investigate preheating dynamics, focusing on particle production via parametric resonance in quantum-corrected ⁴ ϕ 4 inflation with a non-minimal coupling to gravity. In this scenario, the inflaton ϕ couples to an additional scalar χ through an interaction g^2 ^2 ^2 g 2 ϕ 2