Exploring the Hubble Parameter Tension with Early Dark Energy

Abstract

The recent measurements of the cosmic microwave background (CMB) temperature and polarization spectra are in excellent agreement with the standard cosmological model (ΛCDM) (Planck Collaboration et al., 2018). However, there is a discrepancy between some local measurements of the Hubble constant H0 and the value of H0 inferred from the CMB data. One proposed solution to this tension is the early dark energy (EDE) model which extends the standard cosmological model to include an exotic component which acts as dark energy in the early universe (prior to recombination) and then quickly decays away at later times. In this work, we study the EDE model and the signatures it leaves on cosmological observables. We reanalyze the EDE model with primary CMB data from Planck satellite and Atacama Cosmology Telescope and explore the constraints which can be placed on the parameters of the model, given the current data. We also consider one possible configuration of the planned CMB-S4 experiment and explore how it could be used to further constrain the model.