A look at the Hubble speed from first principles
Abstract
We introduce a novel way of measuring H0 from a combination of independent geometrical datasets, with no need of calibration nor of the choice of a cosmological model. We build on the distance duality relation which sets the ratio of the luminosity and angular diameter distance to a fixed scaling in redshift for any metric theory of gravity with standard photon propagation and constitutes a founding block of any theory describing our Universe. Our method provides the unprecedented possibility of determining H0 from first principles, unleashing the measurement of this fundamental constant from calibration and assumption of a cosmological model. We find H0=69.5 1.7 km/s/Mpc at 68\% C.L. showing that the Hubble constant can be constrained at percent level with minimal assumptions.