Phil Marshall

Phil Marshall showed up today to give the astrophysics seminar. He also attended the CampHogg group meeting. In his seminar, he talked about finding and exploiting strong gravitational lenses in large sky surveys to make precise (and, importantly, accurate) inferences about the expansion history (or redshift—distance relation). He showed that when you are concerned that you might be affected by severe systematics, the best approach is to make your model much more flexible but then learn the relationships among the new nuisance parameters that make the much more flexible model nonetheless still informative. This requires hierarchical inference, which both Marshall and I have been pushing on the community for some years now.

In group meeting, he had the group members talk about the things they are most excited about. Among other things, this got Angus talking about periodograms with much better noise models under the hood and it got Foreman-Mackey talking about linear algebra tricks that might change our lives. Huppenkothen blew Marshall away with her example light-curves from GRS 1915. Marshall himself said he was excited about building a full three-dimensional model of all the mass density inside the Hubble volume, using both weak lensing and large-scale structure simultaneously. He has some ideas about baby steps that might make first projects tractable in the short run.