Multi-field dark energy: cosmic acceleration on a steep potential

TL;DR

This paper explores multi-field dark energy models that enable cosmic acceleration on steep potentials, predicting unique observational signatures such as enhanced structure growth, which could be tested in future surveys.

Contribution

It introduces multi-field dark energy models with non-geodesic trajectories that satisfy swampland constraints and differ from standard models in their perturbation behavior.

Findings

Multi-field models can satisfy swampland constraints.

Dark energy perturbations can lead to enhanced structure growth.

Models are observationally similar to ΛCDM at background level.

Abstract

We argue that dark energy with multiple fields is theoretically well-motivated and predicts distinct observational signatures, in particular when cosmic acceleration takes place along a trajectory that is highly non-geodesic in field space. Such models provide novel physics compared to $\Lambda$CDM and quintessence by allowing cosmic acceleration on steep potentials. From the theoretical point of view, these theories can easily satisfy the conjectured swampland constraints and may in certain cases be technically natural, potential problems which are endemic to standard single-field dark energy. Observationally, we argue that while such multi-field models are likely to be largely indistinguishable from the concordance cosmology at the background level, dark energy perturbations can cluster, leading to an enhanced growth of large-scale structure that may be testable as early as the next generation of cosmological surveys.