Analytic bounds on late-time axion-scalar cosmologies

TL;DR

This paper derives analytical bounds on late-time cosmological solutions involving multiple scalar and pseudoscalar fields with curved field space, aiding model building without solving complex equations.

Contribution

It provides the first analytical, initial-condition-independent bounds on late-time cosmologies with multiple scalar fields and curved field space metrics.

Findings

Bounds are proven analytically without approximations.

Applicable to string compactification models.

Assist in assessing cosmic acceleration viability.

Abstract

The cosmological dynamics of multiple scalar/pseudoscalar fields are difficult to solve, especially when the field-space metric is curved. This presents a challenge in determining whether a given model can support cosmic acceleration, without solving for the on-shell solution. In this work, we present bounds on late-time FLRW-cosmologies in classes of theories that involve arbitrary numbers of scalar and pseudoscalar fields coupled both kinetically (leading to a curved field space metric) and through scalar potentials. Such bounds are proven analytically, independently of initial conditions, with no approximation in the field equations and without referring to explicit solutions. Besides their broad applications to cosmological model building, our bounds can be applied to studying asymptotic cosmologies of certain classes of string compactifications.