Classification of solutions to nonlinear elliptic partial differential equations—a vector field approach
课程摘要
The energy method is a powerful tool for establishing a priori estimates for elliptic partial differential equations; from another perspective, it is the vector field method. Inspired by geometric problems such as the Bochner technique and the Obata method, the vector field method for elliptic PDEs has been applied to various equations since the 1970s, such as the applications to second-order elliptic equations by Gidas-Spruck and Serrin-Zou, as well as our recent new insights into sub-elliptic equations on the Heisenberg group and a class of fourth-order elliptic equations. We will give a brief review of the history and techniques of the related problems, and elaborate in detail on their applications to extremal functions and best constants for the relevant second-order and fourth-order Sobolev inequalities.