In article ,
"Jonathan Thornburg [remove -animal to reply]"
writes:

The preprint is 1909.06712

Two additional preprints are at
https://arxiv.org/abs/1907.04869 and
https://arxiv.org/abs/1910.06306
These report direct measurements of gravitational lens distances
rather than a recalibration of the standard distance ladder.

The lead author Shajib of 06306 spoke here today and showed an
updated version of Fig 12 of the 04869 preprint. The upshot is that
the discrepancy between the local and the CMB measurements of H_0 is
between 4 and 5.7 sigma, depending on how conservative one wants to
be about assumptions. The impression I got is that either there's a
systematic error somewhere or there's new physics. The local H_0 is
based on two independent methods -- distance ladder and lensing -- so
big systematic errors in local H_0 seem unlikely. The CMB H_0 is
based on Planck with WMAP having given an H_0 value more consistent
with the local one. "New physics" could be something as simple as
time-varying dark energy, but for now it's too soon to say much.

One other note from the talk: it takes an expert modeler about 8 months
to a year to model a single lens system. Shajib and others are trying
to automate the modeling, but until that's done, measuring a large
sample of lenses will be labor-intensive. Even then, it will be
cpu-intensive. Shahib mentioned 1 million cpu-hours for his model of
DES J0408-53545354, and about 40 lenses are needed to give the desired
precision of local H_0.

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