Late-time approaches to the Hubble tension deforming H(z), worsen the growth tension

Many late-time approaches for the solution of the Hubble tension use late time smooth deformations of the Hubble expansion rate H(z) of the Planck18/Lambda CDM best fit to match the locally measured value of H-0 while effectively keeping the comoving distance to the last scattering surface and Omega(0m)h(2) fixed to maintain consistency with Planck CMB measurements. A well-known problem of these approaches is that they worsen the fit to low z distance probes. Here, we show that another problem of these approaches is that they worsen the level of the Omega(0m) - sigma(8) growth tension. We use the generic class of CPL parametrizations corresponding to evolving dark energy equation of state parameter w(z) = w(0) + w(1) z/1+z with local measurements H-0 prior and identify the pairs (w(0), w(1)) that satisfy this condition. This is a generic class of smooth deformations of H(z) that are designed to address the Hubble tension. We show that for these models the growth tension between dynamical probe data and CMB constraints is worse than the corresponding tension of the standard Planck18/Lambda CDM model. We justify this feature using a full numerical solution of the growth equation and fit to the data, as well as by using an approximate analytic approach. The problem does not affect recent proposed solutions of the Hubble crisis involving a SnIa intrinsic luminosity transition at z(t) similar or equal to 0.01.

Automated summary

Many late-time approaches for solving the Hubble tension involve smooth deformations of the Hubble expansion rate to match local measurements, but this can worsen the fit to low z distance probes and the Omega(0m) - sigma(8) growth tension. By studying parametric models, it is found that the growth tension introduced by these models is worse than the standard model, highlighting a potential issue with these solutions.