Maintenance and suppression of chaos by weak harmonic perturbations: A unified view

General results concerning maintenance or enhancement of chaos are presente d for dissipative systems subjected to two harmonic perturbations (one chao s inducing and the other chaos enhancing). The connection with previous res ults on chaos suppression is also discussed in a general setting. It is dem onstrated that, in general, a second harmonic perturbation can reliably pla y an enhancer or inhibitor role by solely adjusting its initial phase. Nume rical results indicate that general theoretical findings concerning periodi c chaos-inducing perturbations also work for aperiodic chaos-inducing pertu rbations, and in arrays of identical chaotic coupled oscillators.