Higher index focus–focus singularities in the Jaynes–Cummings–Gaudin model: Symplectic invariants and monodromy

Abstract

We study the symplectic geometry of the Jaynes–Cummings–Gaudin model with n = 2 m − 1 spins. We show that there are focus–focus singularities of maximal Williamson type ( 0 , 0 , m ) . We construct the linearized normal flows in the vicinity of such a point and show that soliton type solutions extend them globally on the critical torus. This allows us to compute the leading term in the Taylor expansion of the symplectic invariants and the monodromy associated to this singularity.