I meant the videos and slides of the talks of this conference are online. So anyone can watch the talks and discussions

]]>Refraction is not the issue here. The universe is basically transparent to photons.

]]>I agree, just like the Hubble constant 🙃.

We have observed the universe is not a true vacuum. As you stated, “We know that the Universe is not exactly homogeneous and isotropic”

If the refraction index is not isotropic, how can the velocity of light be?

]]>The speed of light in vacuo is constant in general relativity.

]]>There are questions in my mind about the recent lensing results, actually. Specifically about how the combination of the 6 results is done. It will be interesting to see if this result survives serious scrutiny.

]]>*“this is a D_A and not D_L measurement, isn’t it?”*

Yes, but a bit more complicated, as three angular-size distances are involved (between observer and lens, lens and source, and observer and source; in general, the last isn’t the sum of the other two). Also, one has to have an accurate mass model, and there is some degeneracy in that different mass distributions could produce the same observables (angles, flux ratios, etc).

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