Critical fluctuations observed in collective human behaviors

By analyzing order-book data of the foreign exchange market, Empirical facts of real market fluctuations are summarized. Then, we introduce numerical experiments using an artificial market model consisted of algorithmic dealers. Finally, we show that a generalized Langevin equation nearly the critical point is a promising theoretical model which can describe not only microscopic market properties but also macroscopic human behaviors typically observed in the period of hyper-inflation. The origins of both long-tailed distribution of price fluctuations and the dynamical motions of bubbles and crashes will be discussed from the viewpoint of physics.