Self-organized model for information spread in financial markets

A self-organized model with social percolation process is proposed to describe the propagations of information for different trading ways across a social system and the automatic formation of various groups within market traders. Based on the market structure of this model, some stylized observations of real market can be reproduced, including the slow decay of volatility correlations, and the fat tail distribution of price returns which is found to cross over to an exponential-type asymptotic decay in different dimensional systems.Comment: 8 pages with 7 EPS figures, LaTeX2e with EPJ class; Eur. Phys. J. B, in pres

X(3915) and X(4350) as new members in P-wave charmonium family

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly support to explain the newly observed X(3915) and X(4350) as new members in P-wave charmonium family, i.e., $\chi_{c0}^\prime$ for X(3915) and $\chi_{c2}^{\prime\prime}$ for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the $J^{PC}$ quantum numbers of X(3915) and X(4350) must be $0^{++}$ and $2^{++}$ respectively, which provide the important criterion to test P-wave charmonium explanation for X(3915) and X(4350) proposed by this letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and experimental search for them is suggested.Comment: 4 pages, 2 figures, 2 tables. More references and discussions added, typos corrected. Accepted for publication in Phys. Rev. Lett

Power, Levy, Exponential and Gaussian Regimes in Autocatalytic Financial Systems

We study by theoretical analysis and by direct numerical simulation the dynamics of a wide class of asynchronous stochastic systems composed of many autocatalytic degrees of freedom. We describe the generic emergence of truncated power laws in the size distribution of their individual elements. The exponents $\alpha$ of these power laws are time independent and depend only on the way the elements with very small values are treated. These truncated power laws determine the collective time evolution of the system. In particular the global stochastic fluctuations of the system differ from the normal Gaussian noise according to the time and size scales at which these fluctuations are considered. We describe the ranges in which these fluctuations are parameterized respectively by: the Levy regime $\alpha < 2$, the power law decay with large exponent ($\alpha > 2$), and the exponential decay. Finally we relate these results to the large exponent power laws found in the actual behavior of the stock markets and to the exponential cut-off detected in certain recent measurement.Comment: 9 pages with 5 figures; Proceedings of EPS conference "Applications of Physics in Financial Analysis 2", 13 to 15 July 2000 Liege, Belgium (to appear in Eur. Phys. J. B