Revisiting Polynomial Hybrid Inflation: Planck and ACT Compatibility via Radiative Corrections

Abstract

We investigate the impact of one-loop radiative corrections in a non-supersymmetric model of hybrid inflation with a chaotic (polynomial-like) potential,$V(\phi) = V_0 + \lambda_p \phi^p$, in the light of the latest constraints from \textit{Planck} and \textit{Atacama Cosmology Telescope} (ACT) observations. Here, $V_0$ denotes the energy scale of inflation, and $\lambda_p$ is a coupling associated with the polynomial term of power $p$. These corrections can naturally arise from couplings of the inflaton to other matter fields, which also facilitate the reheating process. At the tree level, the predictions of such models for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ typically lie outside the current observational bounds. However, incorporating one-loop radiative corrections modifies the potential to, \[ V(\phi) = V_0 + \lambda_p \phi^p + A \phi^4 \ln (\phi/ \mu), \] where $A$ characterizes the strength of the inflaton's coupling to other fields, and \(\mu\) is an appropriate renormalization scale. This radiatively corrected potential can reconcile the model with the combined \textit{Planck}+ACT data over a suitable range of parameter space explored in this work. In particular, radiative corrections from fermionic loops ($A < 0$) suppress the tensor-to-scalar ratio $r$, while simultaneously yielding a red-tilted spectrum with $n_s < 1$, even for sub-Planckian field excursions. This brings the prediction in line with current observations, while still allowing for potentially detectable signatures of primordial gravitational waves. Furthermore, the inflaton's couplings enable successful reheating and naturally accommodate non-thermal leptogenesis, providing a unified framework for inflation and baryogenesis.