Mutated Hybrid Inflation

TL;DR

The paper presents a two-field hybrid inflation model with a non-trivial inflaton trajectory that yields an unusual potential along inflation. The effective single-field dynamics along the trajectory give $V \simeq \frac{m^2 M^2}{1+\alpha} \approx m^2 M^2\left(1-\frac{2 m^2}{\lambda^2 \phi^2}\right)$ with $\alpha = \frac{2 m^2}{\lambda^2 \phi^2}$ and $\phi^2 \gg \alpha$, leading to slow-roll parameters $V'/V \simeq \frac{2\alpha}{\phi}$, $V''/V \simeq -\frac{6\alpha}{\phi^2}$ and $N \simeq \frac{\phi^2}{8\alpha}$; this yields a spectral index $n \simeq 1 - \frac{3}{2N}$ (≈0.97) and a negligibly small tensor-to-scalar ratio $R \ll 10^{-4}$, with COBE normalization fixing $V^{3/2}/V' \approx 6 \times 10^{-4}$. The model can be embedded in a supersymmetric framework via a superpotential that reproduces the same potential form, connecting $M$ and $m$ to a high-scale $\Lambda$ (e.g., from gaugino condensation) around $10^{13-14}$ GeV, highlighting a concrete link between particle physics scales and inflationary observables.

Abstract

A new model of inflation is described. An unusual form for the inflationary potential is obtained because the inflaton corresponds to a non-trivial path in the configuration space of the two real scalar fields of the model. The model predicts a spectral index $n = 1 - 3/2N \simeq 0.97$ for the density perturbations and negligible gravitational waves.