The symplectic reduction of the linearized Hamiltonian systems at elliptic relative equilibria of four-body problem

Abstract: In this paper, we consider the elliptic relative equilibria of four-body problem. Here we prove that the corresponding linearized Hamiltonian system at such an elliptic relative equilibria of $4$-bodies splits into two independent linear Hamiltonian systems, the first one is the linearized Hamiltonian system of the Kepler $2$-body problem at Kepler elliptic orbit, and the other system is the essential part of the linearized Hamiltonian system, which is given implicitly. The reduction can be applied to the stability problem of such elliptic relative equilibria of four-body problem.