Is there an early Universe solution to Hubble tension?
Abstract
We consider a low redshift (z<0.7) cosmological dataset comprising megamasers, cosmic chronometers, type Ia SNe and BAO, which we bin according to their redshift. For each bin, we read the value of H0 by fitting directly to the flat model. Doing so, we find that H0 descends with redshift, allowing one to fit a line with a non-zero slope of statistical significance 2.1 \, σ. Our analysis rests on the use of cosmic chronometers to break a degeneracy in BAO data and it will be imperative to revisit this feature as data improves. Nevertheless, our results provide the first independent indication of the descending trend reported by the H0LiCOW collaboration. If substantiated going forward, early Universe solutions to the Hubble tension will struggle explaining this trend.