Two-system of a Hamiltonian system
  For a Hamiltonian system in R^{2n}, its two-system is defined in the phase space R^{2n} x sp(2n,R). In a sense, it is a combination of the original system and its system in variations with feedback. We study the Hamiltonian forms of the two-system and its analogs. In particular, we show a relation between the Poisson-Lie bracket on the (dual space to) Lie algebra sp(2n,R) and the canonical bracket. 
M.F. Kondratieva, S.Yu. Sadov