# abstracts

## Piotr Chrusciel (Vienna)

#### Positivity of the Bondi mass

I will present an elementary proof of positivity of Bondi mass for space-times containing smooth light cones.

## Joaquin Perez (Granada)

#### CMC foliations of Euclidean three-space with a countable number of singularlities

It is proven that in any compact oriented $n$-manifold without boundary and Euler characteristic zero, there exists a smooth transversely oriented foliation whose leaves have constant mean curvature for some Riemannian metric in the ambient space.

## Mu-Tao Wang (Columbia)

#### On the center of mass in general relativity

A new definition of the center of mass of an initial data set will be introduced in this talk. The construction is built on our previous work of quasi-local mass and optimal isometric embeddings. This is the first definition that is consistent with the classical dynamical formula p=mc in the nonlinear context of initial data sets evolving by the vacuum Einstein equation. The talk is based on joint work with Po-Ning chen and Shing-Tung Yau.