http://arxiv.org/abs/1910.02978
The current Hubble constant tension is usually presented by comparing constraints on $H_0$ only. However, the post-recombination background cosmic evolution is determined by two parameters in the standard $\Lambda$CDM model, the Hubble constant ($H_0$) and today’s matter energy fraction ($\Omega_{\rm{m}}$). If we therefore compare all constraints individually in the $H_0$-$\Omega_{\rm{m}}$ plane, (1) various constraints can be treated as independently as possible, (2) single-sided constraints are easier to consider, (3) compatibility among different constraints can be viewed in a more robust way, and (4) whether or not a nonstandard model is able to reconcile all constraints in tension can be seen more effectively. We perform a systematic comparison of independent constraints in the $H_0$-$\Omega_{\rm{m}}$ space based on a flat $\Lambda$CDM model. Constraints along different degeneracy directions consistently overlap in one region of the space, with the exception of the local measurement from Cepheid variable-calibrated supernovae. Due to the different responses of individual constraints to a modified model, it is difficult for nonstandard models with modifications at high-, mid- or low-redshifts to reconcile all constraints if none of them have unaccounted-for systematic effects. Based on our analysis, the local measurement is the most outlying and therefore drives the bulk of the tension. This may suggest that the most likely solution to the tension is an alteration to the local result, either due to some previously unseen feature in our local cosmic environment, or some other unknown systematic effect.
W. Lin, K. Mack and L. Hou
Wed, 9 Oct 19
17/64
Comments: 7 pages, 1 figure