To curve, or not to curve: Is curvature-assisted quintessence observationally viable?

TL;DR

This paper investigates whether curvature-assisted quintessence models with steep potentials are compatible with observations, concluding that such models are not observationally viable despite theoretical motivations from string theory constraints.

Contribution

The study provides a dynamical systems and Bayesian analysis showing that curvature-assisted quintessence models with steep potentials are not supported by current cosmological data.

Findings

Steep-potential models are incompatible with observational data.

Curvature effects do not make quintessence models observationally viable.

Results are applicable to both dark energy and inflation scenarios.

Abstract

Single-field models of accelerated expansion with nearly flat potentials, despite being able to provide observationally viable explanations for the early-time cosmic inflation and the late-time cosmic acceleration, are in strong tension with string theory evidence and the associated de Sitter swampland constraints. It has recently been argued that in an open universe, where the spatial curvature is negative (i.e., with $\Omega_k>0$), a new stable fixed point arises, which may lead to viable single-field-based accelerated expansion with an arbitrarily steep potential. Here, we show, through a dynamical systems analysis and a Bayesian statistical inference of cosmological parameters, that the additional cosmological solutions based on the new fixed point do not render steep-potential, single-field, accelerated expansion observationally viable. We mainly focus on quintessence models of dark energy, but we also argue that a similar conclusion can be drawn for cosmic inflation.