Yanyan Li

A harmonic function of one variable is a linear function. A harmonic function of two variables is the real or imaginary part of an analytic function. A harmonic function of n variables is a function u satisfying \frac{\partial^{2}u}{\partial x_{1}^{2...

We study gradient estimates for solutions of divergence form elliptic systems with piecewise smooth coefficients. These systems arise from composite material. We will mention some open problems. This is an expository talk; is accessible to graduate...