Formal integrals for an autonomous Hamiltonian system near an equilibrium point

@article{Giorgilli1978FormalIF,
title={Formal integrals for an autonomous Hamiltonian system near an equilibrium point},
author={A. Giorgilli and L. Galgani},
journal={Celestial mechanics},
year={1978},
volume={17},
pages={267-280}
}

In this paper we give a new method to construct formal integrals for an autonomous Hamiltonian system near an equilibrium point. Our construction is reminiscent of the algorithms introduced by Hori and Deprit; we show however how it presents itself quite naturally if one follows the line of attack of Whittaker, Cherry, and Contopoulos.