Quantum-corrected $$\phi ^{4}$$ 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 $$n_s$$ n s higher than the Planck 2018 baseline, thereby placing conventional attractor-type inflationary models such as Starobinsky $$R^2$$ R 2 and Higgs inflation under increasing tension at the $$\gtrsim 2\sigma $$ ≳ 2 σ level. In this work, we examine quantum-corrected $$\phi ^4$$ ϕ 4 inflation with a non-minimal coupling to gravity. Introducing an anomalous scaling parameter $$\gamma $$ γ to capture quantum corrections to the effective potential, we derive analytic expressions for the inflationary observables $$n_s$$ n s and r . Confronting these predictions with ACT, Planck, and BAO+lensing constraints, we demonstrate that modest values of $$\gamma $$ γ can raise $$n_s$$ n s into the ACT-preferred range while maintaining a strongly suppressed tensor-to-scalar ratio. For instance, with $$N=60$$ N = 60 and $$\gamma \simeq 0.006$$ γ ≃ 0.006 , the model predicts $$n_s\simeq 0.974$$ n s ≃ 0.974 and $$r\simeq 0.007$$ r ≃ 0.007 , in excellent agreement with current bounds. We further investigate preheating dynamics, focusing on particle production via parametric resonance in quantum-corrected $$\phi ^4$$ ϕ 4 inflation with a non-minimal coupling to gravity. In this scenario, the inflaton $$\phi $$ ϕ couples to an additional scalar $$\chi $$ χ through an interaction $$g^{2}\phi ^{2}\chi ^{2}$$ g 2 ϕ 2