Universality of multi-field $\alpha$-attractors

TL;DR

This paper demonstrates that multi-field $ ext{alpha}$-attractor models with hyperbolic geometry have stable inflationary predictions, resilient to potential modifications, and extend to various $ ext{alpha}$ values, supporting multi-field inflation's observational viability.

Contribution

It shows the double attractor behavior in multi-field $ ext{alpha}$-attractors with hyperbolic moduli space and extends universality of predictions to a broader class of potentials.

Findings

Predictions are stable under potential modifications.

Universality extends to $ ext{alpha} eq 1/3$ with general potentials.

Supports multi-field inflation compatibility with observations.

Abstract

We study a particular version of the theory of cosmological $\alpha$-attractors with $\alpha=1/3$, in which both the dilaton (inflaton) field and the axion field are light during inflation. The kinetic terms in this theory originate from maximal $\mathcal{N}=4$ superconformal symmetry and from maximal $\mathcal{N}=8$ supergravity. We show that because of the underlying hyperbolic geometry of the moduli space in this theory, it exhibits double attractor behavior: their cosmological predictions are stable not only with respect to significant modifications of the dilaton potential, but also with respect to significant modifications of the axion potential: $n_s\simeq 1-{2\over N}$, $r\simeq {4\over N^2}$. We also show that the universality of predictions extends to other values of $\alpha \lesssim {\cal O}(1)$ with general two-field potentials that may or may not have an embedding in supergravity. Our results support the idea that inflation involving multiple, not stabilized, light fields on a hyperbolic manifold may be compatible with current observational constraints for a broad class of potentials.