MaxEnt2013, day 3

I spoke at MaxEnt2013 today, in a short astronomy session that included also Ensslin (MPA), Frean (Wellington), and Brewer. Brewer spoke about our project to fully marginalize out catalogs, and Frean showed some exceedingly general methods for source discovery in data streams, applied (among other things) to astronomical data. I pitched a project to him at lunch about predicting or automatically inspecting survey data as it comes off of telescopes, which would be a beautiful extension of his work. Ensslin showed awesome reconstructions of astrophysical fields (especially the magnetic field in the Galaxy) from sparse data samples (rotation measures, in this case). He uses ideas from field theory to go beyond the Gaussian Process.

There were many valuable talks; too many to mention. Stand-outs for me included a talk by Hutter (ANU) about things that overlap my crazy paper. He was arguing for a message-length approach to selecting theories, especially huge theories of everything. He made the good point that the message must include both the initial conditions and a description of the position of the observer. Hutter describes himself as a mathematical philosopher. Lineweaver (ANU) argued passionately that the Universe is not a fluctuation away from a high-entropy state (I agree) and Goyal (Albany) argued that exchangeability can be used to prove that the universe can only contain fermions and bosons (nothing else). On the latter, I would like to understand it better; I certainly grew up learning the opposite: I learned that this was an additional postulate. Wood (ANU) gave a nice overview of probabilistic topic models and their value and limitations.

After lunch, there were break-out sessions, and we guided the (very well attended) astronomical one to things where Brewer, Murray, and I overlap. We talked about combining information from images taken at different times, through different bandpasses, and with very different calibration properties. The issues are very different if you have the multiple images or if you just have catalogs. Many good ideas came up, including many that I had (nearly) forgotten from my Gaia paper. In the end, we didn't resolve anything but we specified a very sensible project, which is to figure out how one might construct catalog outputs such that the catalogs can be combined to produce inferences that are almost as good as the inferences you get from working with the images directly. Very sensible! And very related to abortive projects I have started with Marshall.

At the end of a long day, Huppenkothen (Amsterdam) was showing Murray and me bursts from Fermi observations of a magnetar, and discussing ways we might fit the data with some kind of process (Gaussian or dictionary). We accreted Brewer and Frean and then challenged ourselves to produce a result by midnight. After a monster hack session we succeeded; we hope to be able to use what we have to constrain rise times (or make some new discovery) in these kinds of bursts.