It was a low-research day today. But I did get in a short and valuable discussion of CMB foregrounds with Boris Leistedt (NYU). The approach I want to pursue is to make a latent-variable model, which posits a set of scalar fields, and nonlinear functions that convert them into (high resolution) maps, that are compared to the data through the relevant beams. I think this will (almost provably) beat current approaches. I also had some conversations with Bedell about optimization. We are trying to fit for stellar spectra and radial velocities, and (as usual) we are finding that out-of-the-box optimizers don't work well!