Closed Reeb orbits on contact type hypersurfaces in $T^{\ast }{S}^n$

Abstract

In this paper, it is proved that under dynamically convex condition, there exist at least $[\frac{n+1}{2}]$ closed Reeb orbits on a closed contact type hypersurface in $T^{\ast }{S}^n$ enclosing the zero section and bounding a simply connected Liouville domain. Furthermore, if the contact form is non-degenerate and has finitely many closed Reeb orbits, then there exist at least two irrationally elliptic closed Reeb orbits.