The HADES seminar on Tuesday, October 14th, will be at 3:30pm in Room 740.

Speaker: Zachary Lee

Abstract: The Nonlinear Schrödinger Equation (NLS) arises in various physical contexts, notably in models of Bose–Einstein condensation and nonlinear optics. I will begin by outlining these motivations and by presenting several heuristics—scaling, dispersion, and symmetry—that shed light on the qualitative behavior of its solutions. I will then turn to a rigorous analysis based on the Duhamel formulation of the equation, together with Strichartz estimates, conservation laws, and Morawetz inequalities, which provide global control for data in the defocusing case. In the final part of the talk, I will describe how these techniques can be adapted below the energy space using almost conservation laws (the I-method), and present a new global existence result for the one-dimensional defocusing septic NLS for a class of discontinuous and unbounded initial data.