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Complex Systems

   Fractional Brownian processes have been proposed as a mathematical model for a wide diversity of stochastic phenomena occurring in real extended physical systems exhibiting different degrees of correlation. The variance at large t scales as a power law, s2 ~ t2H, where H is the Hurst exponent, ranging from 0 to 1. The value H=0.5 corresponds to the ordinary uncorrelated Brownian motion, while H<0.5 and H>0.5 correspond respectively to anticorrelated and correlated signals. The analysis of the Hurst exponent is nowadays considered a practical instrument in fields as biophysics (DNA sequence, gait fluctuations), econophysics, cloud breaking and many others. For example, one can discriminate heartbeat intervals of healthy and sick hearts on the basis of the value of H. Stock price volatility shows a degree of persistence larger than that of the return series (H = 0.5), a fact which is exploited when practical investment tools have to be developed. The validation of climate models is based on the analysis of long-term correlation of atmospheric series. In order for the above mentioned classifications to be reliable, several techniques have been thus proposed with the main purpose to extract as accurate as possible values of the Hurst exponent from the data set. Among the number of different techniques that have been proposed to estimate the correlation exponent of fractal stochastic signals we only mention the spectral analysis, the correlograms and semivariograms, the rescaled range analysis, the Fano factor, the Allan variance, the Detrended Fluctuation Analysis and very recently the Detrended Moving Average analysis. These techniques calculate appropriate statistical functions over the signal in the time or in the frequency domain. We are investigating possible estensions and applications of these techniques.

A. Carbone, B.M. Chiaia, B. Frigo, C. Turk,
Multiscale Modelling of Snow Microstructure
Int. J. of Multiscale Comput. Engin. (2012)


S. Arianos, A. Carbone, C. Turk
Self-similarity of higher order moving averages [PDF]
Phys. Rev. E 84, 046113 (2011)


A. Carbone, B.M. Chiaia, B. Frigo, C. Turk
Snow metamorphism: a fractal approach
Int. J. for Multisc. Comp. Eng. (2010)


C. Turk, A. Carbone, B.M. Chiaia
Fractal Heterogeneous Media [PDF]
Phys. Rev. E 81, 026706-1-7 (2010)


A. Carbone, B.M. Chiaia, B. Frigo, C. Turk
Fractal Model for Snow
Mater. Sc. For. 638-642, pp. 2555-2560 (2010)


S. Arianos and A.Carbone
Cross-correlation of long-range correlated series [PDF]
J. Stat. Mech: Theory and Experiment P03037, (2009)


S. Arianos, E. Bompard, A. Carbone and F. Xue
Power Grids Vulnerability: A Complex Network Approach [PDF]
Chaos 19, 013119 (2009)


A.Carbone
Algorithm to estimate the Hurst exponent of high-dimensional fractals
Phys. Rev. E 76, (2007) [PDF]


S. Arianos and A.Carbone
Detrending Moving Average (DMA) Algorithm: a closed form approximation of the scaling law [PDF]
Physica A 382, 9 (2007)


A.Carbone and H.E. Stanley
Scaling properties and entropy of long range correlated series [PDF]
Physica A 384, 21 (2007)


L. Xu, P. Ch. Ivanov, C. Zhi, K. Hu, A. Carbone, H. E. Stanley
Quantifying signals with power-law correlations
Phys. Rev. E, 71, 051101, (2005) [PDF]


A.Carbone, G. Castelli and H. E. Stanley
Analysis of the clusters formed by the moving average of a long-range correlated stochastic series
Phys. Rev. E, 69, 026105, (2004) [PDF]


A.Carbone, G. Castelli and H. E. Stanley
Time-Dependent Hurst Exponent in Financial Time Series
Physica A, 344, 267, (2004) [PDF]


A.Carbone and H. E. Stanley
Directed Self-Organized Critical Patterns Emerging from Fractional Brownian Paths
Physica A, 340, 544, (2004) [PDF]


A.Carbone and G. Castelli
Scaling of long-range correlated noisy signals: application to financial markets
Noise in Complex Systems and Stochastic Dynamics, L. Schimansky-Geier, D. Abbott, A. Neiman, C. Van den Broeck, Eds.,
Proc. of SPIE, 407, 5114 (2003) [PDF]


E.Alessio, A.Carbone , G.Castelli, V.Frappietro
Second-order moving average and scaling of stochastic time series,
Eur. J. Phys. B, 27, 197, (2002) [PDF]


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