Phenomenological Gravitational Phase Transition: Early and Late
  Modifications
  In this work we generalize the idea of a gravitational phase transition or
GPT at late times to allow for a modified gravity scenario in the early
universe as well. The original GPT was shown to simultaneously relax the $H_0$
and $\sigma_8$ tensions and {\it Planck} internal inconsistencies. However, the
primary results from GPT predictions implied disagreement with the data from
the baryonic acoustic oscillations (BAO). Here we investigate whether the
generalized GPT scenario could address the Hubble tension in the presence of
the BAO data as well. We find that, despite the vastly enlarged gravitational
parameter space, the BAO data strongly prefer the $\Lambda$CDM paradigm with a
low inferred Hubble constant, $68.03\pm 0.76 $ km/s/Mpc, in tension with the
local $H_0$ measurements from Riess et al., $H_0=74.03\pm 1.42$ km/s/Mpc. This
failure of the generalized GPT scenario to host the P18-BAO-R19 trio is of
significance and noticeably shrinks the space of possible gravitational
solutions to the Hubble tension.
