Orateur
Description
Early dark energy (EDE) is a popular extension of the $\Lambda$CDM model, which alleviates the Hubble tension by reducing the sound horizon at recombination. The updated Planck high-$\ell$ likelihood (NPIPE), however, places strong constraints on such models.
In this talk, I will present a model with two non-interacting EDE fields active at different redshifts, inspired by the string Axiverse. Compared to standard EDE, the extra freedom in the two-field model allows the energy boost to spread out over a broader redshift range, which results in an improved fit to high-$\ell$ Planck NPIPE data and, in turn, reduces the Hubble tension. I will also show models with more than two fields, to highlight the statistical artifacts of adding too many degrees of freedom.
The main takeaway is this: in light of Planck NPIPE, a rich pre-recombination history, whether it be 2-field EDE or something else, is an interesting contender for the Hubble tension.