Does Hubble tension signal a breakdown in FLRW cosmology?

The tension between early and late Universe probes of the Hubble constant has motivated various new FLRW cosmologies. Here, we reanalyse the Hubble tension with a recent age of the Universe constraint. This allows us to restrict attention to matter and a dark energy sector that we treat without assuming a specific model. Assuming analyticity of the Hubble parameter H(z), and a generic low redshift modification to flat ?CDM, we find that low redshift data (z less than or similar to 2.5) and well-motivated priors only permit a dark energy sector close to the cosmological constant ?. This restriction rules out late Universe modifications within FLRW. We show that early Universe physics that alters the sound horizon can yield an upper limit of H (0) similar to 71 +/- 1 km s(-1) Mpc(-1). Since various local determinations may be converging to H (0) similar to 73 km s(-1) Mpc(-1), a breakdown of the FLRW framework is a plausible resolution. We outline how future data, in particular strongly lensed quasar data, could also provide further confirmations of such a resolution.

Automated summary

The study focuses on reanalyzing the Hubble tension with a recent age of the Universe constraint, finding that low redshift data and well-motivated priors only permit a dark energy sector close to the cosmological constant, ruling out late Universe modifications within FLRW. Future data, especially strongly lensed quasar data, could provide further confirmation of this resolution.