H0 ex machina: Vacuum metamorphosis and beyond H0

We do not solve tensions with concordance cosmology; we do obtain H-0 approximate to 74 km/s/Mpc from CMB+BAO+SN data in our model, but that is not the point. Discrepancies in Hubble constant values obtained by various astrophysical probes should not be viewed in isolation. While one can resolve at least some of the differences through either an early time transition or late time transition in the expansion rate, these introduce other changes. We advocate a holistic approach, using a wide variety of cosmic data, rather than focusing on one number, H-0. Vacuum metamorphosis, a late time transition physically motivated by quantum gravitational effects and with the same number of parameters as Lambda CDM, can successfully give a high H-0 value from cosmic microwave background data but fails when combined with multiple distance probes. We also explore the influence of spatial curvature, and of a conjoined analysis of cosmic expansion and growth. (c) 2020 Elsevier B.V. All rights reserved.