L. Ferrari et Cde. Boschi, Nonautonomous and nonlinear effects in generalized classical oscillators: A boundedness theorem, PHYS REV E, 62(3), 2000, pp. R3039-R3042
The phenomenon of exponential instability, arising in certain nonautonomous
linear oscillators, motivates the question about the boundedness of amplit
ude and energy of the oscillators describing many physical situations. We p
resent a rigorous result ensuring the boundedness for a class of generalize
d classical oscillators, characterized by symmetric potentials with only on
e equilibrium point. The key elements turn out to be the oscillating nature
of the solutions and the presence of an autonomous part in the potential,
diverging more than quadratically with the coordinate.