Lee Hwa Chung theorem

The Lee Hwa Chung theorem is a theorem in symplectic topology.

The statement is as follows. Let M be a symplectic manifold with symplectic form ω. Let ${\displaystyle \alpha }$ be a differential k-form on M which is invariant for all Hamiltonian vector fields. Then:

• If k is odd, ${\displaystyle \alpha =0.}$

• If k is even, ${\displaystyle \alpha =c\times \omega ^{\wedge {\frac {k}{2}}}}$, where ${\displaystyle c\in \mathbb {R} .}$