Geodesics of norms on the contactomorphisms group of $\mathbb{R}^{2n} \times S^1$

TL;DR

This paper characterizes geodesics in the contactomorphism group of n  S^1 under various norms, linking the norms to Hamiltonian functions and showing their unboundedness.

Contribution

It provides a characterization of geodesics for different norms on the contactomorphism group of n old S^1, relating them to Hamiltonian functions.

Findings

Geodesics are characterized by conditions on Hamiltonian functions.

Norms of contactomorphisms along geodesics relate to maximum Hamiltonian values.

All considered norms are shown to be unbounded.

Abstract

We prove that some paths of contactomorphisms of $\mathbb{R}^{2n} \times S^1$ endowed with its standard contact structure are geodesics for different norms defined on the identity component of the group of compactly supported contactomorphisms and its universal cover. We characterize these geodesics by giving conditions on the Hamiltonian functions that generate them. For every norm considered we show that the norm of a contactomorphism that is the time-one of such a geodesic can be expressed in terms of the maximum of the absolute value of the corresponding Hamiltonian function. In particular we recover the fact that these norms are unbounded