Lipschitz Continuous Solutions of Elliptic Equations of the Form ...(Du)D²u = 0.
We prove comparison principles for viscosity solutions of nonlinear second order, uniformly elliptic equations, which extend previous results of P. L. Lions, R. Jensen and H. Ishii. Some basic pointwise estimates for classical solutions are also extended to continuous viscosity solutions.
We assign a measure to an upper semicontinuous function which is subharmonic with respect to the mean curvature operator, so that it agrees with the mean curvature of its graph when the function is smooth. We prove that the measure is weakly continuous with respect to almost everywhere convergence. We also establish a sharp Harnack inequality for the minimal surface equation, which is crucial for our proof of the weak continuity. As an application we prove the existence of weak solutions to the...
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