EFFECT OF NOISE ON COUPLED CHAOTIC SYSTEMS

The effect of noise in inducing order on various chaotically evolving systems is reviewed, with special emphasis on systems consisting of co upled chaotic elements. In many situations it is observed that the unc oupled elements when driven by identical noise, show synchronization p henomena where chaotic trajectories exponentially converge towards a s ingle noisy trajectory, independent of the initial conditions. In a ra ndom neural network, with infinite range coupling, chaos is suppressed due to noise and the system evolves towards a fixed point. Spatiotemp oral stochastic resonance phenomenon has been observed in a square arr ay of coupled threshold devices where a temporal characteristic of the system resonates at a given noise strength. In a chaotically evolving coupled map lattice with the logistic map as local dynamics and drive n by identical noise at each site, we report that the number of struct ures (a structure is a group of neighbouring lattice sites for values of the variable follow which the certain predefined pattern) follows a power-law decay with the length of the structure. An interesting phen omenon, which we call stochastic coherence, is also reported in which the abundance and lifetimes of these structures show characteristic pe aks at some intermediate noise strength.