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Do the Early Galaxies observed by JWST disagree with Planck's CMB polarization measurements? Published: 6/13/2023 5:03:28 PM Updated: 6/13/2023 5:03:28 PM

Paper abstract: The recent observations from the James Webb Space Telescope have led to asurprising discovery of a significant density of massive galaxies with massesof M \ge 10^{10.5} M_{\odot} at redshifts of approximately z~ 10. Thiscorresponds to a stellar mass density of roughly \rho_*~ 10^6 M_{\odot}Mpc^{-3}. Despite making conservative assumptions regarding galaxy formation,this finding may not be compatible with the standard \LambdaCDM cosmologythat is favored by observations of CMB Anisotropies from the Planck satellite.In this paper, we confirm the substantial discrepancy with Planck's resultswithin the \LambdaCDM framework. Assuming a value of \epsilon=0.2 for theefficiency of converting baryons into stars, we indeed find that the\LambdaCDM model is excluded at more than 99.7 \% confidence level (C.L.).An even more significant exclusion is found for \epsilon ~ 0.1, while abetter agreement, but still in tension at more than 95 \%, is obtained for\epsilon =0.32. This tension, as already discussed in the literature, couldarise either from systematics in the JWST measurements or from new physics.Here, as a last-ditch effort, we point out that disregarding the large angularscale polarization obtained by Planck, which allows for significantly largervalues of the matter clustering parameter \sigma_8, could lead to betteragreement between Planck and JWST within the \LambdaCDM framework.Interestingly, the model compatible with Planck temperature-only data and JWSTobservation also favors a higher Hubble constant H_0=69.0\pm1.1 km/s/Mpc at68\% C.L., in better agreement with observations based on SN-Ia luminositydistances.