Broken scale invariance, $\alpha$-attractors and vector impurity

TL;DR

This paper explores how spontaneous breaking of scale symmetry in $eta$-attractor models constrains the $oldsymbol{ extit{ extalpha}}$ parameter, affecting inflationary predictions and post-inflationary universe dynamics.

Contribution

It demonstrates that stability considerations restrict $ extit{ extalpha}$ to a narrow range, linking inflationary predictions with post-inflationary universe behavior.

Findings

$ extit{ extalpha}$ constrained to 5/6 < $ extit{ extalpha}$ < 1.

Inflationary predictions align with Planck data within this range.

Different $ extit{ extalpha}$ values lead to distinct post-inflationary scenarios.

Abstract

We show that if the $\alpha$-attractor model is realized by the spontaneous breaking of the scale symmetry, then the stability and the dynamics of the vector field that gauges the scale symmetry can severely constrain the $\alpha$-parameter as $5/6 < \alpha < 1$ restricting the inflationary predictions in a very tiny region in the $n_s - r$ plane that are in great agreement with the latest Planck data. Although the different values of $\alpha$ do not make a tangible difference for $n_s$ and $r$, they provide radically different scenarios for the post-inflationary dynamics which determines the standard BBN processes and the large scale isotropy of the universe.