Spitzer peak-up, exact cosmology

Michael Joyce (Paris) gave a great group-meeting talk in which he showed that he can perform exact analyses of discrete N-body simulations for finite particle density, in the linear regime, and explain the output of numerical codes. He focused on differences between numerical simulations and the real world that arise from discreteness. All this matters for precision cosmology.

In the afternoon, Ed Bertschinger (MIT) used the nice property that the growth of fluctuations in the Universe can be calculated in a picture in which you treat each (sufficiently large) fluctuation as its own little FRW Universe to calculate growth of structure in some non-Einstein gravity theories. He showed some beautiful exact solutions in a suite of departures from GR.

In the early morning I worked on my tesselations for our Spitzer proposal. I had to reverse engineer the IRS peak-up star flux criteria, because I have to make my observation plans automatically with code, not manually with the (nice) observation planning tool.