Amplification of weak signals and stochastic resonance via on-off intermittency with symmetry breaking

Noise-free stochastic resonance at an interior crisis

We report on the observation of noise-free stochastic resonance in an externally driven diode resonator close to an interior crisis. At sufficiently high excitation amplitudes the diode resonator shows a strange attractor which after the collision with an unstable period-three orbit exhibits crisis-induced intermittency. In the intermittency regime the system jumps between the previously stable chaotic attractor and the phase space region which has been made accessible by the crisis. This random process can be used to amplify a weak periodic signal through the mechanism of stochastic resonance. In contrast to conventional stochastic resonance no external noise is needed. The chaotic intrinsic dynamics plays the role of the stochastic forcing. Our data obtained from the diode resonator are compared with numerical simulations of the logistic map where a similar crisis-induced intermittency is observed.

Lever-assisted two-noise stochastic resonance

A critical interplay of two correlated noises in a nonlinear symmetrical two-well potential system is experimentally demonstrated. One state can become completely noise free, leading to an infinite Kramers time. If an independent lever breaks the potential symmetry, stochastic resonance is recovered. In this new regime, we obtain a plateau, i.e., a high signal-to-noise ratio even for vanishing forcing signals.

Transition from intermittency to periodicity in lag synchronization in coupled Rössler oscillators

The dynamical and statistical behavior of lag synchronization in two coupled self-sustained chaotic Rössler oscillators is reexamined. The lack of uniqueness in the conventional characterization of lag synchronization based on the similarity function has caused much skepticism about the existence of lag synchronization. We provide an evidence that the emergence of lag synchronization is associated with the transition from on-off intermittency to a periodic structure in the laminar phase distribution.

Attractor bifurcation and on-off intermittency

We analyze the bifurcation of an attractor in a system of multiplicatively coupled maps. It is shown that the phenomenon can be characterized by on-off intermittency and it is rigorously described by the on-off intermittency in the presence of noise through the concept of a virtually invariant manifold. Presenting numerical results which conform our claims, we elucidate the role of on-off intermittency in bifurcation phenomena.

Stochastic multiresonance in a chaotic map with fractal basins of attraction

Noise-free stochastic resonance in a chaotic kicked spin model at the edge of the attractor merging crisis is considered. The output signal reflects the occurrence of crisis-induced jumps between the two parts of the attractor. As the control parameter-the amplitude of the magnetic field pulses-is varied, the signal-to-noise ratio shows plateaus and multiple maxima, thus stochastic multiresonance is observed. It is shown that the multiresonance occurs due to a fractal structure of the precritical attractors and their basins. In the adiabatic approximation theoretical expression for the signal-to-noise ratio is derived, based on the theory of oscillations in average crisis-induced transient lifetimes. Numerical and theoretical results agree quantitatively just above the threshold for crisis and qualitatively in a wide range of the control parameter.

Amplification of near-resonant signals via stochastic resonance in a chaotic CO2 laser

We show experimentally and numerically that a chaotic CO2 laser with modulated losses operating in the region of an intermittency resulting from the band-merging crisis can serve as an amplifier of near-resonant signals, i.e., signals with a frequency close to the first subharmonic frequency, via deterministic stochastic resonance. The mechanism underlying stochastic resonance in this case is a synchronization of the random switching events between two chaotic repellers after the band-merging crisis with near-resonant signals at the detuning frequency. We demonstrate experimentally that the gain factor in chaos is larger than near the first period-doubling bifurcation by a factor of 2. Numerical results obtained in a two-level rate-equation model are in good agreement with the experimental ones.