Abstract
The local expansion rate of the Universe is parametrized by the Hubble
constant, $H_0$, the ratio between recession velocity and distance. Different
techniques lead to inconsistent estimates of $H_0$. Observations of Type Ia
supernovae (SNe) can be used to measure $H_0$, but this requires an external
calibrator to convert relative distances to absolute ones. We use the angular
diameter distance to strong gravitational lenses as a suitable calibrator,
which is only weakly sensitive to cosmological assumptions. We determine the
angular diameter distances to two gravitational lenses, $810^+160_-130$ and
$1230^+180_-150$~Mpc, at redshifts of $z=0.295$ and $0.6304$. Using these
absolute distances to calibrate 740 previously-measured relative distances to
SNe, we measure the Hubble constant to be $H_0=82.4^+8.4_-8.3 ~\rm
km\,s^-1\,Mpc^-1$.
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