An approach for obtaining integrable Hamiltonians from Poisson-commuting polynomial families

TL;DR

This paper presents a general method for identifying Poisson-commuting Hamiltonians that are integrable via separation of variables, introduces new integrable models including superintegrable and isochronous systems, and uncovers a novel algebraic structure in their Poisson brackets.

Contribution

The paper introduces a broad approach to find integrable Hamiltonians from polynomial families, proves superintegrability of the goldfish Hamiltonian, and identifies new integrable and isochronous systems.

Findings

Goldfish Hamiltonian is maximally superintegrable.

Explicit integration of Hamiltonians commuting with goldfish.

Discovery of new isochronous integrable Hamiltonians.

Abstract

We discuss a general approach permitting the identification of a broad class of sets of Poisson-commuting Hamiltonians, which are integrable in the sense of Liouville. It is shown that all such Hamiltonians can be solved explicitly by a separation of variables {\em Ansatz}. The method leads in particular to a proof that the so-called "goldfish" Hamiltonian is maximally superintegrable, and leads to an elementary identification of a full set of integrals of motion. The Hamiltonians in involution with the "goldfish" Hamiltonian are also explicitly integrated. New integrable Hamiltonians are identified, among which some have the property of being isochronous, that is, that all their orbits have the same period. Finally, a peculiar structure is identified in the Poisson brackets between the elementary symmetric functions and the set of Hamiltonians commuting with the "goldfish" Hamiltonian: these can be expressed as products between elementary symmetric functions and Hamiltonians. The structure displays an invariance property with respect to one element, and has both a symmetry and a closure property. The meaning of this structure is not altogether clear to the author, but it turns out to be a powerful tool.