Manuel Fernandez-Guasti

arXiv2025

On the four-body limaçon choreography: maximal superintegrability and choreographic fragmentation

In this paper, as a continuation of [Fernandez-Guasti, \textit{Celest Mech Dyn Astron} 137, 4 (2025)], we demonstrate the maximal superintegrability of the reduced Hamiltonian, which governs the four-body choreographic planar motion along the trisectrix limaçon (resembling a folded figure eight), in the six-dimensional space of relative motion. The pairwise interaction potential $V(r_{ij})$ among the four bodies is a quadratic expression in the relative distances $r_{ij}$, with a combination of positive and negative coefficients. The corresponding eleven integrals of motion in the Liouville-Arnold sense are presented explicitly. Specifically, it is shown that the reduced Hamiltonian admits complete separation of variables in Jacobi-like variables. The emergence of this choreography is not a direct consequence of maximal superintegrability. Rather, it originates from the existence of \textit{particular integrals} and the phenomenon of \textit{particular involution}. We also provide a detailed analysis of the fragmentation of a general four-body choreographic motion into two isomorphic two-body choreographies, as well as the reverse process, namely, the fusion of two-body choreographies into a four-body configuration. This model combines choreographic motion with maximal superintegrability, a seldom-studied interplay in classical mechanics.

math-ph↗

arXiv2025

N-body choreographies on a p-limacon curve

We consider an $N$--body problem under a harmonic potential of the form $\frac{1}{2}\sum κ_{jl} |q_j-q_l|^2$. A $p$-limaçon curve is a planar curve parametrized by $t$ given by $a(\cos t,\sin t)+b(\cos pt, \sin pt)$, where $a,b\in \mathbb{R}$, $p \in \mathbb{Z}$, and $t \in [0,2π]$. We study $N$-body choreographic motions constrained to a $p$-limaçon curve and establish necessary and sufficient conditions for their existence. Specifically, we prove that choreographic motions exist if and only if $p/N, (p \pm 1)/N \notin \mathbb{Z}$. Under an additional symmetry assumption on the force coefficients, we further refine these conditions. We also analyze the occurrence of collisions, showing that for given $p$ and $N$, at most $2(N-1)$ choices of $a/b$ lead to collisions. Furthermore, we find additional conserved quantities.

math.DS↗