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arXiv · 2509.17179

Multifield Cosmology and the Dark Universe

Lilia Anguelova
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Abstract

Multifield models, arising from multiple scalars interacting with gravity, provide a rich theoretical framework for addressing fundamental problems in modern cosmology. A key role in this regard is played by the so called rapid turn regime, which is characterized by background solutions with strongly non-geodesic field-space trajectories. We review the implications of this regime for a number of problems relevant for cosmological inflation, dark matter and dark energy. We focus, in more detail, on a class of exact rapid-turn solutions that give a model of dynamical dark energy. In this model, the sound speed of the dark energy perturbations is reduced compared to the speed of light, which leads to observational differences from a cosmological constant even for an equation-of-state parameter very close to -1. Furthermore, this model holds promise for the simultaneous alleviation of two prominent cosmological tensions.

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Lilia Anguelova. 2025-09-21. Multifield Cosmology and the Dark Universe. https://doi.org/10.1088/1742-6596%2F3152%2F1%2F012022

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