quantum gravity, causality, planets per star

Two seminars today: Gia Dvali (NYU and LMU) gave the lunchtime brown-bag talk, about the possible interaction of quantum gravity with the axion and neutrino sectors. The idea is that the "strong CP problem" implies that some invariant of the gluon field is so small that the interaction between gluons and the graviton field could actually dominate or be dynamically significant. It was only moderately incomprehensible!

Late in the day, Jennifer Hill (NYU) spoke about causal inference in the social sciences. She talked about the Rubin formulation of causality, and the problems of having observational (rather than randomized) data. She argued the point that almost all important questions in science are causal questions, so we have to face this! Her methods involve fitting incredibly flexible and complex models to the parts of the problem she doesn't care about to reveal the residual correlations that she does care about.

Early in the day I spoke with Tim Morton (Princeton) about inferring planets-per-star rate statistics from data. The methods in the literature seem highly biased (and naive, as they involve "transforming" rather than modeling the data). We talked about next steps.

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