Mean curvature flow. Lecture 4

Application of mean curvature flow to General  Relativity" We study 2-dimensional spheres moving in asymptotically flat 3-manifolds of non-negative  scalar curvature, which appear as spacelike  slices of a Lorentzian manifold modelling  isolated gravitating systems. It is shown that mean curvature flow can help to  understand the concept of mass and center of  mass in such systems.