On Kostant-Kirillov Symplectic Structure and Quasi-Poisson Structures of the Euler-Arnold Systems

The concept of symplectic structure emerged between 1808 to 1810 through the works of Lagrange and Poisson on the trajectory of the planets of the solar system. In order to explain the variation of the orbital parameters, they introduced the symplectic structure associated to the manifold describing the states of the system and a fundamental operation on functions called Poisson’s bracket. But, the latter also comes from the Hamiltonian formalism which does not automatically lead to a Poisson structure. Although contrary to the Riemannian case, not every manifold necessarily admits a symplectic structure including even dimensional manifolds. The aim of this paper is to show the interaction between the Kostant-Kirillov symplectic structure and quasi-Poisson structures coming from the Euler-Arnold systems. The Lie algebra theoretical approach based on the Kostant-Kirillov coadjoint action will allow us to obtain a class of the quasi-Poisson structures resulting from the characterization of the Hamiltonian system and to prove some results on the Kostant-Kirillov symplectic structure in the quasi-Poisson context.