New Early Dark Energy

Florian Niedermann, Martin S. Sloth

Research output: Contribution to journalJournal articleResearchpeer-review

New measurements of the expansion rate of the universe have plunged the standard model of cosmology into a severe crisis. In this letter we propose a simple resolution to the problem. We propose that a first order phase transition in a dark sector in the early universe, before recombination, can resolve the problem. This will lead to a short phase of a New Early Dark Energy (New EDE) component and can explain the observations. Fitting our model to measurements of the Cosmic Microwave Background, Baryonic Acoustic Oscillations, and supernovae yields a significant improvement of the best fit compared with the standard cosmological model without EDE at the cost of only two extra parameters. We find the mean value of the present Hubble parameter in the New EDE model to be $H_0=70.4 \pm 1.0 ~\textrm{km}\, \textrm{s}^{-1}\, \textrm{Mpc}^{-1}$.