transparency scoop, velocities, testing GR

More and Bovy found papers today that—to some extent—scoop our result on the transparency of the Universe with baryon acoustic feature and type Ia supernovae. We did some re-tooling to emphasize the new aspects of our work in this context.

Bovy and I discussed at length various issues related to the determination of the velocity field from Hipparcos. Bovy has implemented a beautiful system that determines the error-deconvolved distribution of velocities, even in the face of the issue that each data point has a different error. We discussed using his fit to the velocity field to predict the results of radial velocity surveys.

Bhuvnesh Jain (Penn) gave a great astro seminar on testing gravity using the comparison of lensing and kinematic / dynamical measures of the potential. He featured Adam Bolton's strong lenses as among the best tests of this, although Bolton's test is at smaller length scales (kpc) than the scales of interest to most cosmologists (Mpc to Gpc). Jain made a very good argument that if you want to test GR, you have to work at all scales and with all techniques; the different cosmological tests can only be combined or ranked if you believe GR.

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