The day started with a conversation with Elisabeth Andersson (NYU) about possible projects. We tentatively decided to look for resonant planets in the Kepler data. I sent her the Luger paper on TRAPPIST-1.
Before lunch, there was a great Astro Seminar by Marcel Schmittfull (IAS) about using the non-linearities in the growth of large-scale structure to improve measurements of cosmological parameters. He made two clear points (to me): One is that the first-order "reconstruction" methods used to run back the clock on nonlinear clustering can be substantially improved upon (and even small improvements can lead to large improvements in cosmological parameter estimation). The other is that there is as much information about cosmological parameters in the skewness as the variance (ish!). After his talk I asked about improving reconstruction even further using machine learning, which led to a conversation with Marc Williamson (NYU) about a possible pilot project.
In the afternoon, after a talk about crazy black-hole ideas from Ram Brustein (Ben-Gurion), Matt Kleban (NYU) and I discussed the great difficulty of seeing strong-field corrections to general relativity in gravitational-wave measurements. The problem is that the radiation signal is dominated by activity well outside the Schwarzschild radius: Things close to the horizon are highly time-dilated and red-shifted and so don't add hugely to the strong parts of the signal. Most observable signatures of departures from GR are probably already ruled out by other observations! With the standard model, dark matter, dark energy, and GR all looking like they have no observational issues, fundamental physics is looking a little boring right now!
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