Inflation from Minkowski Space

TL;DR

This paper introduces scalar models coupled to gravity that connect an inflationary universe to a low-curvature spacetime, violating the null energy condition and producing observable signatures like large tensor-to-scalar ratios and nongaussianities.

Contribution

It presents a new class of symmetry-based scalar models that enable stable, smooth transitions from inflation to low-curvature spacetimes, extending galilean genesis scenarios.

Findings

Models can produce large tensor-to-scalar ratios.

Models generate sizeable equilateral nongaussianities.

The approach ensures quantum robustness and stability.

Abstract

We propose a class of scalar models that, once coupled to gravity, lead to cosmologies that smoothly and stably connect an inflationary quasi-de Sitter universe to a low, or even zero-curvature, maximally symmetric spacetime in the asymptotic past, strongly violating the null energy condition ($\dot H\gg H^2$) at intermediate times. The models are deformations of the conformal galileon lagrangian and are therefore based on symmetries, both exact and approximate, that ensure the quantum robustness of the whole picture. The resulting cosmological backgrounds can be viewed as regularized extensions of the galilean genesis scenario, or, equivalently, as `early-time-complete' realizations of inflation. The late-time inflationary dynamics possesses phenomenologically interesting properties: it can produce a large tensor-to-scalar ratio within the regime of validity of the effective field theory and can lead to sizeable equilateral nongaussianities.