Konwersatorium im. Leopolda Infelda

It is a major aim of mathematical relativity tofind and describe natural geometric structures that modelclassical physical concepts for isolated gravitating systems, such asmass, center of mass and momentum. The lecture explainshow suitable foliations of space-time and geometric variationalproblems such as the isoperimetric inequality can be usedto define a useful and geometrically invariant concept forthe total mass of a system. The lecture also describes howelliptic and parabolic systems of geometric PDEs are used tojustify these concepts in the context of Einsteins equations.