For both quasar structure functions and Jagannath's project on tidal streams, I am playing around a lot with non-trivial variance tensors to insert into Gaussian probability distribution functions. On the quasars, I am trying to make a very pedagogical introduction to the idea that the structure function—a model of quasar variance—should be cast in terms of Gaussian processes—a set of general models for variance. This was Bovy's good idea; it makes all sorts of new kinds of data analyses possible and all sorts of existing observations more useful. On the streams, we are modeling observational uncertainty (which is simple in distance, transverse angles, radial velocity, and transverse angular velocity but complex in position–velocity space) in six-dimensional phase space, so that our cold-stream data analysis has a realistic description. The short-term goal is to establish a method for fitting streams that is justified in terms of probabilistic inference.
After lunch, Rory Holmes (MPIA) led a discussion of Euclid calibration and observing strategy, because the MPIA is part of a team proposing to operate part of that mission.