1/f noise in a nonequilibrium phase transition: Experiment and mathematical model

The results of an experimental investigation of a high-power source of broad-band 1/f noise, which can be generated in a system of two interacting nonequilibrium phase transitions, are presented. This process takes place when a normal conductor-superconductor phase transition is superposed on the critical liquid-vapor transition in a boiling coolant. A mathematical model describing a nonequilibrium phase transition in a complicated nonlinear system with two interacting order parameters, which involves the conversion of white noise into stochastic fluctuations of the order parameters with 1/f and 1/f(2) spectra, is proposed. The properties of the model fluctuations with a 1/f spectrum agree qualitatively with the experimentally observed properties. A characteristic difference between the model fluctuations with a 1/f(2) spectrum and random walks is also noted. (C) 1998 American Institute of Physics. [S1063-7761(98)01305-5].