R. Chacon, NATURAL SYMMETRIES AND REGULARIZATION BY MEANS OF WEAK PARAMETRIC MODULATIONS IN THE FORCED PENDULUM, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 52(3), 1995, pp. 2330-2337
The suppression of chaos in the driven pendulum due to a small paramet
ric modulating term is studied theoretically with Melnikov's method, a
nd the results are compared with those from classical perturbation the
ory. I obtained coherent results for the initial phase differences bet
ween the two modulations for which the chaotic dynamics is regularized
. It is also shown that these values are compatible with the surviving
natural symmetry under the parametric modulation.