Disentangling cosmic distance tensions with early and late dark energy

Abstract

Recent cosmological data reveal tension between parameters inferred from measurements of the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and supernovae (SN) under $\Lambda$CDM. Typical dynamical dark energy parameterizations (such as $w_0{w}_a$) that seek to jointly resolve these tensions have an equation of state parameter that crosses into the phantom regime, leading to potential instabilities for physical models. We show that the BAO (early-time) and SN (late-time) sides of the tension can instead be treated independently. Early dark energy (EDE) can reduce the tension between CMB-BAO data by changing the calibration of the sound horizon at the drag epoch $r_d$, with a $\Delta {\chi }^2=-9.4$ relative to $\Lambda$CDM, raising $H_0$ to 70.87 $\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$. EDE alone cannot bring consistency between CMB, BAO, and SN data, but combining with a thawing-quintessence component of dark energy reduces tensions between the three datasets, with $\Delta {\chi }^2=-12.6$ relative to $\Lambda$CDM without a phantom component, vs. $\Delta {\chi }^2=-15.8$ for $w_0{w}_a$ with one. We consider different SN datasets, using the most recent DES Dovekie catalog as our default while assessing differences with the original DESY5 and Pantheon+ catalogs. While the significance of adding thawing quintessence changes, the EDE solution to the CMB-BAO tension remains nearly unaffected. Moreover, though we do not include direct Hubble constant measurements in these $\Delta {\chi }^2$ values, the EDE solution reduces the Hubble tension with the Local Distance Network value from $7\sigma$ in $\Lambda$CDM to $2-3\sigma$ depending on the SN dataset, nominally the equivalent of an extra $\Delta {\chi }^2\sim -40$ or more.