Mass and geometric inequalities Guofang Wang (Freiburg) Abstract: In this talk, we first use the Gauss-Bonnet-Chern scalar curvature to introduce a new mass, Gauss-Bonnet-Chern mass, for asymptotically flat manifolds and for asymptotically hyperbolic manifolds. Then we establish optimal isoperimetric type inequalities to prove a Penrose inequality for this new mass, for a class of graphical manifolds. (This is a joint work with Yuxin Ge and Jie Wu)