Early Dark Energy can Resolve the Hubble Tension
Abstract
Early dark energy (EDE) that behaves like a cosmological constant at early times (redshifts z ≳3000 ) and then dilutes away like radiation or faster at later times can solve the Hubble tension. In these models, the sound horizon at decoupling is reduced resulting in a larger value of the Hubble parameter H_{0} inferred from the cosmic microwave background (CMB). We consider two physical models for this EDE, one involving an oscillating scalar field and another a slowly rolling field. We perform a detailed calculation of the evolution of perturbations in these models. A Markov Chain Monte Carlo search of the parameter space for the EDE parameters, in conjunction with the standard cosmological parameters, identifies regions in which H_{0} inferred from Planck CMB data agrees with the SH0ES local measurement. In these cosmologies, current baryon acoustic oscillation and supernova data are described as successfully as in the cold dark matter model with a cosmological constant, while the fit to Planck data is slightly improved. Future CMB and largescalestructure surveys will further probe this scenario.
 Publication:

Physical Review Letters
 Pub Date:
 June 2019
 DOI:
 10.1103/PhysRevLett.122.221301
 arXiv:
 arXiv:1811.04083
 Bibcode:
 2019PhRvL.122v1301P
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 v1: 4p+appendix, 3 figures. v2: small changes, notably estimates of bayesian evidence. matches the version published in PRL