On the number of P-invariant closed characteristics on partially   symmetric compact convex hypersurfaces in ${\bf R}^{2n}$
  In this paper, let $n\geq2$ be an integer, $P=diag(-I_{n-\kappa},I_\kappa,-I_{n-\kappa},I_\kappa)$ for some integer $\kappa\in[0, n)$, and $\Sigma \subset {\bf R}^{2n}$ be a partially symmetric compact convex hypersurface, i.e., $x\in \Sigma$ implies $Px\in\Sigma$. We prove that if $\Sigma$ is $(r,R)$-pinched with $\frac{R}{r}<\sqrt{2}$, then there exist at least $n-\kappa$ geometrically distinct P-symmetric closed characteristics on $\Sigma$, as a consequence, $\Sigma$ carry at least $n$ geometrically distinct P-invariant closed characteristics. 
Hui Liu and Duanzhi Zhang
math.DS