Horndeski Genesis: strong coupling and absence thereof

TL;DR

This paper investigates the classical consistency of Genesis cosmology within Horndeski theory, addressing strong coupling issues and identifying parameter ranges where classical analysis remains valid despite early-time instabilities.

Contribution

It demonstrates that classical field theory can be valid during early Genesis in Horndeski models, even with vanishing effective Planck mass, under specific parameter conditions.

Findings

Classical analysis is valid in certain parameter regimes.

Early Genesis can be free of instabilities.

Strong coupling issues can be mitigated in Horndeski models.

Abstract

We consider Genesis in the Horndeski theory as an alternative to or completion of the inflationary scenario. One of the options free of instabilities at all cosmological epochs is the one in which the early Genesis is naively plagued with strong coupling. We address this issue to see whether classical field theory description of the background evolution at this early stage is consistent, nevertheless. We argue that, indeed, despite the fact that the effective Plank mass tends to zero at early time asymptotics, the classical analysis is legitimate in a certain range of Lagrangian parameters.