A universal attractor for inflation at strong coupling

TL;DR

A novel nonminimal coupling between gravity and the inflaton sector is introduced and for large values of this coupling all models asymptote to a universal attractor, located in the "sweet spot" of parameter values that are preferred by Planck's recent results.

Abstract

We introduce a novel non-minimal coupling between gravity and the inflaton sector. Remarkably, for large values of this coupling all models asymptote to a universal attractor. This behavior is independent of the original scalar potential and generalizes the attractor in the phi^4 theory with non-minimal coupling to gravity. The attractor is located in the `sweet spot' of Planck's recent results.

Figures (2)

• Figure 1: The $\xi$-dependence of $(n_s,r)$ on a linear and a logarithmic scale for different chaotic models with $n=(2/3, 1, 2, 3, 4, 6, 8)$, from right to left, for 60 e-foldings. The points on the logarithmic scale (lower panel) correspond to $\log(\xi)=(-1, \ldots, 1)$, from top down. The convergence to the attractor point occurs almost instantly for $n \geq 4$.
• Figure 2: The $\xi$-dependence of $(n_s,r)$ on a linear and a logarithmic scale for different natural models with $f=(5, 5.25, 5.75, 6.33, 7.5, 10, 100)$ (in decreasing redshift) for 60 e-folds. The points correspond to $\log(\xi)=(0,\ldots,3)$.