The Physics Colloquium today was by Jasna Brujic (NYU) who talked about biomimetic packing: This is creation of artificial tissue from artifical
cells, non-living analogs of biological systems. I learned things about random packing and the statistical properties of heterogeneous materials. In particular, I was interested to learn that although you can hold a (frictionless, perfect) sphere with four points of contact, if you have a frustrated random solid packing of (frictionless, perfect) spheres, each sphere will have, on average, six points of contact. As you remove points of contact, the bulk and shear moduli drop to zero.
I discussed fast imaging (lucky imaging) with Federica Bianco (NYU), Foreman-Mackey, and Fadely. Bianco is interested in data analysis methods that lead to unbiased photometry; this is hard when the PSF is a very strong function of time and space, as it is in fast imaging. We have some ideas, and some code that is half-done.
Guangtun Zhu (JHU) dropped in to discuss recent work. He showed beautiful spectral models of quasars, beautiful average absorption spectra, and beautiful galaxy–gas cross-correlation functions from quasar absorption spectra. We argued that he could, on the one hand, analyze detailed issues with SDSS spectroscopic calibration and, on the other hand, determine the fraction of the cosmic matter density in a range of atomic species. Nice diversity there!