Self-oscillations, undamped

To avoid this handicap, Boersch and coworkers 2) used coupled resonators. The first active laser cavitiy generates the radiation whose absorption is to be measured. The probe is placed in a second cavity, which is coupled to the first one and which is undamped by an active medium just below the threshold for self-oscillation. This arrangement enables changes in the refractive index as small as An 10 ° or absorption coefficients down to a 10 to be detected. 

Two types of attractors were known since the times of Poincare points or closed curves (limit cycles). The third type was discovered in 1971 [60]. It is so-called strange attractor , which can exist in three- and more-dimensional systems. In accordance with these three known types of attractors, three different kind of system s behaviour are possible after bifurcation (1) transition into a new stable steady state (2) undamped self-oscillations, and (3) chaotic regime (turbulence). 

Staying within a class of mono- and bimolecular reactions, we thus can apply to them safely the technique of many-point densities developed in Chapter 5. To establish a new criterion insuring the self-organisation, we consider below the autowave processes (if any) occurring in the simplest systems -the Lotka and Lotka-Volterra models [22-24] (Section 2.1.1). It should be reminded only that standard chemical kinetics denies their ability to selforganisation either due to the absence of undamped oscillations (the Lotka model) or since these oscillations are unstable (the Lotka-Volterra model). 

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