The focus will be on various methods, tools and ideas that are used by mathematicians working with PDE.
Maximum/comparison principle (various forms), Hopf ’s lemma.
Harnack’s inequality, boundary Harnack.
Fundamental solution , Green’s function, Green’s integral identities.
Elliptic estimates, Alexandroff ’s, B., P., estimates.
Barriers, regularity up to the boundary.
Sobolev spaces: Weak/strong convergence, imbedding, Compactness arguments.
Notion of solutions: W^k,m, viscosity, classical in C^k .
Rearrangements.
Qualitative theory: Symmetry, Moving plane methods, reflections, inversions, sliding methods.
Geometric measure theory: Scaling, Blow up, flatness, measure theoretic normal, densities, structure theorems.
Hausdorff dimension, packing measures.
Free boundaries and applications