title: Noise-induced volatility of collective dynamics.
abstract: 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.
authors.affiliation: Chair of Entrepreneurial Risks, D-MTEC, ETH Zurich, CH-8092 Zurich, Switzerland.
authors.forename: Georges
authors.initials: G
authors.lastname: Harras
authors.forename: Claudio J
authors.initials: CJ
authors.lastname: Tessone
authors.forename: Didier
authors.initials: D
authors.lastname: Sornette
mesh_terms: D000818:Animals; D003198:Computer Simulation; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D018448:Models, Immunological; D015233:Models, Statistical