Proper group actions and symplectic stratified spaces

L. Bates, E. Lerman

Let $(M,\omega )$ be a Hamiltonian $G$-space with a momentum map $F:M\to {\mathfrak{g}}^{\ast }$. It is well-known that if $\alpha$ is a regular value of $F$ and $G$ acts freely and properly on the lev…