The GBC mass for asymptotically hyperbolic manifolds

The paper consists of two parts. In the first part, by using the Gauss-Bonnet curvature, which is a natural generalization of the scalar curvature, we introduce a higher order mass, the Gauss-Bonnet-Chern mass m^{\H}_k, for asymptotically hyperbolic manifolds and show that it is a geometric invariant. Moreover, we prove a positive mass theorem for this new mass for asymptotically hyperbolic graphs and establish a relationship between the corresponding Penrose type inequality for this mass and weighted Alexandrov-Fenchel inequalities in the hyperbolic space \H^n. In the second part, we establish these weighted Alexandrov-Fenchel inequalities in \H^n for any horospherical convex hypersurface $\Sigma$. As an application, we obtain an optimal Penrose type inequality for the new mass defined in the first part for asymptotically hyperbolic graphs with a horizon type boundary $\Sigma$, provided that a dominant energy condition $\tilde L_k\ge0$ holds. Both inequalities are optimal.