Non-oscillating early dark energy and quintessence from α-attractors

Abstract

Early dark energy (EDE) is one of the most promising possibilities in order to resolve the Hubble tension: the discrepancy between the locally measured and cosmologically inferred values of the Hubble constant. In this paper we propose a toy model of unified EDE and late dark energy (DE), driven by a scalar field in the context of $\alpha$-attractors. The field provides an injection of a subdominant dark energy component near matter-radiation equality, and redshifts away shortly after via free-fall, later refreezing to become late-time DE at the present day. Using reasonable estimates of the current constraints on EDE from the literature, we find that the parameter space is narrow but viable, making our model readily falsifiable. Since our model is non-oscillatory, the density of the field decays faster than the usual oscillatory EDE, thereby possibly achieving better agreement with observations.