SPT-3G D1: Axion Early Dark Energy with CMB experiments and DESI (2507.23355v1)

Abstract: We present the most up-to-date constraints on axion early dark energy (AEDE) from cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements. In particular, we assess the impact of data from ground-based CMB experiments, the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT) -- both with and without $Planck$ -- on constraints on AEDE. We also highlight the impact that BAO information from the Dark Energy Spectroscopic Instrument (DESI) has on these constraints. From CMB data alone, we do not find statistically significant evidence for the presence of AEDE, and we find only moderate reduction in the Hubble tension. From the latest SPT data alone, we find the maximal fractional contribution of AEDE to the cosmic energy budget is $f_{\rm EDE}\,<\,0.12$ at $95\,$% confidence level (CL), and the Hubble tension between the SPT and SH0ES results is reduced to the $2.3\,\sigma$ level. When combining the latest SPT, ACT, and $Planck$ datasets, we find $f_{\rm EDE}\,<\,0.091$ at $95\,$% CL and the Hubble tension at the $3.3\, \sigma$ level. In contrast, adding DESI data to the CMB datasets results in mild preference for AEDE and, in some cases, non-negligible reduction in the Hubble tension. From SPT+DESI, we find $f_{\rm EDE}\,=\,0.081^{+0.037}_{-0.052}$ at $68\,$% CL, and the Hubble tension reduces to $1.5\,\sigma$. From the combination of DESI with all three CMB experiments, we get $f_{\rm EDE}\,=\, 0.071^{+0.035}_{-0.038}$ at $68\,$% CL and a weak preference for AEDE over $\Lambda$CDM. This data combination, in turn, reduces the Hubble tension to $2.3\, \sigma$. We highlight that this shift in parameters when adding the DESI dataset is a manifestation of the discrepancy currently present between DESI and CMB experiments in the concordance model $\Lambda$CDM.