Symplectic invariants of elliptic fixed points
Symplectic invariants of elliptic fixed points
To the germ of an area-preserving diffeomorphism at an elliptic fixed point, we associate the germ of Mather's minimal action. This yields a strictly convex function which is symplectically invariant and comprises the classical Birkhoff invariants as the Taylor coefficients of its convex conjugate. In addition, however, the minimal action …