An interacting-agent model of financial markets from the viewpoint of   nonextensive statistical mechanics
  In this paper we present an interacting-agent model of stock markets. We describe a stock market through an Ising-like model in order to formulate the tendency of traders getting to be influenced by the other traders' investment attitudes [1], and formulate the traders' decision-making regarding investment as the maximum entropy principle for nonextensive entropy. We demonstrate that the equilibrium probability distribution function of the traders' investment attitude is the {\it q-exponential distribution}. We also show that the power-law distribution of the volatility of price fluctuations, which is often demonstrated in empirical studies, can be explained naturally by our model which is based on the collective crowd behavior of many interacting agents. 
Taisei Kaizoji