On the Hubble expansion in a Big Bang quantum cosmology

The Hubble expansion of the Universe is considered in the classical limit of a Big Bang quantum cosmology. In an IR-consistent coupling to the the bare cosmological constant, we infer a dark energy as a relic of the Big Bang by loss of time-translation invariance on a Hubble time-scale. This dark energy is identified with the trace J of the Schouten tensor permitting an analytic solution H ( z ) . Anchored by the Baryonic Accoustic Oscillations , J CDM predicts a Hubble constant H 0 = 6 / 5 H 0 Λ alleviating H 0 -tension between the Local Distance Ladder and H 0 Λ in ΛCDM, whose dark energy Λ is a constant. Emulated by w ( a ) Λ CDM, a CAMB analysis shows a J CDM fit to the Planck 2018 C l T T power spectrum on par with ΛCDM with small positive curvature consistent with Planck -ΛCDM with no extra relativistic degrees of freedom. In late-time cosmology, J CDM is also consistent with the BAO recently measured by DESI. J CDM offers a novel framework to address H 0 -tension, predicting background quantities consistent with the uncertainties in BAO measurements and early-Universe observations. It predicts a deceleration parameter q 0 ≃ − 1 , that may be tested with upcoming low-redshift galaxy surveys.