Existence of closed characteristics on compact convex hypersurfaces in   $\R^{2n}
  In this paper, we prove there exist at least $[\frac{n+1}{2}]+1$ geometrically distinct closed characteristics on every compact convex hypersurface $\Sg$ in $\R^{2n}$. Moreover, there exist at least $[\frac{n}{2}]+1$ geometrically distinct non-hyperbolic closed characteristics on $\Sg$ in $\R^{2n}$ provided the number of geometrically distinct closed characteristics on $\Sg$ is finite. 
Wei Wang
math.SG