Speaker
Description
Multifield cosmology, arising from the interaction of multiple scalar fields with gravity, can lead to qualitatively new features, when the background solutions have strongly non-geodesic trajectories in field space. This is the so called rapid-turn regime. We outline the reasons why rapid-turning can produce novel effects relevant for inflation, dark matter or dark energy. Then we focus on a particular class of multifield dark energy models in the rapid-turn regime. We show that the speed of sound of the dark energy perturbations, in these models, is reduced compared to the speed of light, which can have implications for the large-scale clustering of matter. Furthermore, we argue that this class of models holds significant promise for alleviating the Hubble and $\sigma_8$ tensions simultaneously.
