Kirillov structures and reduction of Hamiltonian systems by scaling and standard symmetries

TL;DR

This paper explores the reduction of symplectic Hamiltonian systems using scaling and standard symmetries, leading to Kirillov Hamiltonian systems, with results applicable to Lie groups and their Lie-Poisson structures.

Contribution

It demonstrates that reduction by commuting scaling and standard symmetries yields equivalent Kirillov Hamiltonian systems and provides a reconstruction method for such systems.

Findings

Reduction by scaling and standard symmetries produces Kirillov Hamiltonian systems.

Order of reduction (scaling then standard or vice versa) does not affect the outcome.

Application to Lie groups yields Kirillov versions of Lie-Poisson structures.

Abstract

In this paper, we discuss the reduction of symplectic Hamiltonian systems by scaling and standard symmetries which commute. We prove that such a reduction process produces a so-called Kirillov Hamiltonian system. Moreover, we show that if we reduce first by the scaling symmetries and then by the standard ones or in the opposite order, we obtain equivalent Kirillov Hamiltonian systems. In the particular case when the configuration space of the symplectic Hamiltonian system is a Lie group G, which coincides with the symmetry group, the reduced structure is an interesting Kirillov version of the Lie-Poisson structure on the dual space of the Lie algebra of G. We also discuss a reconstruction process for symplectic Hamiltonian systems which admit a scaling symmetry. All the previous results are illustrated in detail with some interesting examples.