Canonical Hubble-Tension-Resolving Early Dark Energy Cosmologies Are Inconsistent with the Lyman-α Forest

Current cosmological data exhibit discordance between indirect and some direct inferences of the present-day expansion rate H-0. Early dark energy (EDE), which briefly increases the cosmic expansion rate prior to recombination, is a leading scenario for resolving this "Hubble tension" while preserving a good fit to cosmic microwave background (CMB) data. However, this comes at the cost of changes in parameters that affect structure formation in the late-time universe, including the spectral index of scalar perturbations n(s). Here, we present the first constraints on axionlike EDE using data from the Lyman-alpha forest, i.e., absorption lines imprinted in background quasar spectra by neutral hydrogen gas along the line of sight. We consider two independent measurements of the one-dimensional Ly alpha forest flux power spectrum from the combine these with a baseline dataset comprised of Planck CMB data and baryon acoustic oscillation (BAO) measurements. Combining the eBOSS Ly alpha data with the CMB and BAO dataset reduces the 95% confidence level (C.L.) upper bound on the maximum fractional contribution of EDE to the cosmic energy budget fEDE from 0.07 to 0.03 and constrains H-0 = 67.9 thorn 0.4 a posteriori value H0 = 67.9 km/s/Mpc. Similar results are obtained for the MIKE/HIRES and X-Shooter Ly alpha data. Our Ly alpha-based EDE constraints yield H0 values that are in > 4 sigma tension with the SH0ES distance-ladder measurement and are driven by the preference of the Ly alpha forest data for ns values lower than those required by EDE cosmologies that fit Planck CMB data. Taken at face value, the Ly alpha forest severely constrains canonical EDE models that could resolve the Hubble tension.