vary all the exposure times!

Ruth Angus showed up for a few days, and we talked out the first steps to make an argument for taking time-series data with variable exposure times. We all know that non-uniform spacing of data helps with frequency recovery in time series; our new intuition is that non-uniform exposure time will help as well, especially for very high frequencies (short periods). We are setting up tests now with Kepler data but an eye to challenging the TESS mission to biting a big, scary bullet.

After complaining for the millionth time about PCA (and my loyal reader—who turns out to be Todd Small at The Climate Corporation—knows I love to hate on the PCA), Foreman-Mackey and I finally decided to fire up the robust PCA or PCP method from compressed sensing (not the badly-re-named "robust PCA" in the astronomy literature). The fundamental paper is Candès et al; the method has no free parameters, and the paper includes ridiculously simple pseudo-code. It looks like it absolutely rocks, and obviates all masking or interpolation of missing or bad data!

At lunch, Gabriele Veneziano (Paris, NYU) spoke about graviton–graviton interactions and causality constraints. Question that came up in the talk: If a particle suffers a negative time delay (like the opposite of a gravitational time delay), can you necessarily therefore build a time machine? That's something to dine out on.

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