The structure of phase space close to fixed points in a 4D symplectic
  map
  We study the dynamics in the neighborhood of fixed points in a 4D symplectic
map by means of the color and rotation method. We compare the results with the
corresponding cases encountered in galactic type potentials and we find that
they are in good agreement. The fact that the 4D phase space close to fixed
points is similar to the 4D representations of the surfaces of section close to
periodic orbits, indicates an archetypical 4D pattern for each kind of
(in)stability, not only in 3D autonomous Hamiltonian systems with galactic type
potentials but for a larger class of dynamical systems. This pattern is
successfully visualized with the method we use in the paper.
