"Noise-induced volatility" refers to a phenomenon of increased level of
fluctuations in the collective dynamics of bistable units in the presence of a
rapidly varying external signal, and intermediate noise levels. The
archetypical signature of this phenomenon is that --beyond the increase in the
level of fluctuations-- the response of the system becomes uncorrelated with
the external driving force, making it different from stochastic resonance.
Numerical simulations and an analytical theory of a stochastic dynamical
version of the Ising model on regular and random networks demonstrate the
ubiquity and robustness of this phenomenon, which is argued to be a possible
cause of excess volatility in financial markets, of enhanced effective
temperatures in a variety of out-of-equilibrium systems and of strong selective
responses of immune systems of complex biological organisms. Extensive
numerical simulations are compared with a mean-field theory for different
network topologies
