Hr. Lewis et al., TIME-DEPENDENT PERTURBATION-THEORY FOR THE CONSTRUCTION OF INVARIANTSOF HAMILTONIAN-SYSTEMS, Physics letters. A, 215(3-4), 1996, pp. 160-166
A time-dependent perturbation theory is presented for iteratively cons
tructing invariants for a Hamiltonian consisting of a time-independent
zeroth-order term plus a time-dependent perturbation. The procedure i
nvolves only a single canonical transformation and small divisors can
be avoided. The Mathieu equation is treated as an example.