Globally and locally attractive solutions for quasi-periodically forced systems

We consider a class of differential equations, , with ω∈Rd, describing one-dimensional dissipative systems subject to a periodic or quasi-periodic (Diophantine) forcing. We study existence and properties of trajectories with the same quasi-periodicity as the forcing. For g(x)=x2p+1, p∈N, we show that, when the dissipation coefficient is large enough, there is only one such trajectory and that it describes a global attractor. In the case of more general nonlinearities, including g(x)=x² (describing the varactor equation), we find that there is at least one trajectory which describes a local attractor.