Journal of Statistical Physics, Vol. 44, Nos. 5/6, 1986. p. 907-920.
The anharmonic oscillator under combined sinusoidal and white noise excitation is studied using the Gaussian closure approximation. The mean response and the steady-state variance of the system is obtained by the WKBJ
approximation and also by the Fokker Planck equation. The multiple steady-state solutions are obtained and their stability analysis is presented. Numerical results are obtained for a particular set of system parameters. The theoretical results are compared with a digital simulation study to bring out the usefulness of the present approximate theory.