Flattening the Inflaton's Potential with Quantum Corrections

TL;DR

The paper addresses how to achieve slow-roll inflation without fine-tuning by flattening the inflaton potential through quantum corrections. It introduces an RG-improved potential $V(\phi)=V_0\left[1-\tfrac{1}{2} f(\epsilon\ln\phi)\phi^2\right]$ that develops a flat region near a special field value $\phi_*$ defined by $f_*+\frac{\epsilon}{2}f'_* =0$, with $\epsilon\ln\phi_*=-1$. Depending on the sign of $f'_*,$ the model can realize slow-roll toward a true vacuum (or via a hybrid exit) and may experience eternal inflation near $\phi_*$. The spectral index $n$ is found to be $n=1+2V''/V=1-2\epsilon f'_* (\ln(\phi/\phi_*)+1)$, and while natural parameter choices often yield too small a value, specific parameter selections can produce $n\sim 0.8$, illustrating a potentially observable scale dependence. Overall, the work provides a theoretically motivated mechanism for flattening the inflaton potential using quantum corrections, with implications for inflation models embedded in string-theoretic frameworks.

Abstract

I show that a classical scalar potential with $ V''/V \sim 1 $ can be sufficiently flattened by quantum corrections to give rise to slow-roll inflation. This provides perhaps the simplest way to generate an inflationary potential without fine tuning. The most natural implementation of this idea produces an unviably small spectral index, but, for example, $ n \sim 0.8 $ can be obtained in other implementations.