Contactomorphisms with $L^2$ metric on stream functions

Abstract

Here we investigate some geometric properties of the contactomorphism group ${\mathcal{D}}_{\theta }(M)$ of a compact contact manifold with the $L^2$ metric on the stream functions. Viewing this group as a generalization to the $\mathcal{D}(S^1)$, the diffeomorphism group of the circle, we show that its sectional curvature is always non-negative and that the the Riemannian exponential map is not locally $C^1$. Lastly, we show that the quantomorphism group is a totally geodesic submanifold of ${\mathcal{D}}_{\theta }(M)$ and talk about its Riemannian submersion onto the symplectomorphism group of the Boothby-Wang quotient of $M$.