This award is made as part of the FY 2017 Mathematical Sciences Postdoctoral Research Fellowships Program. Each of the fellowships supports a research and training project at a host institution in the mathematical sciences, including applications to other disciplines, under the mentorship of a sponsoring scientist. The title of the project for this fellowship to Casey L. Kelleher is "Harmonic Maps and Yang-Mills Fields: Relationships and Applications." The host institution for the fellowship is Princeton University, and the sponsoring scientist is Gang Tian.