Journal of Statistical Physics

, Volume 122, Issue 1, pp 137–167

Nonergodicity of a Time Series Obeying Lévy Statistics

  • Gennady Margolin
  • Eli Barkai

DOI: 10.1007/s10955-005-8076-9

Cite this article as:
Margolin, G. & Barkai, E. J Stat Phys (2006) 122: 137. doi:10.1007/s10955-005-8076-9


Time-averaged autocorrelation functions of a dichotomous random process switching between 1 and 0 and governed by wide power law sojourn time distribution are studied. Such a process, called a Lévy walk, describes dynamical behaviors of many physical systems, fluorescence intermittency of semiconductor nanocrystals under continuous laser illumination being one example. When the mean sojourn time diverges the process is non-ergodic. In that case, the time average autocorrelation function is not equal to the ensemble averaged autocorrelation function, instead it remains random even in the limit of long measurement time. Several approximations for the distribution of this random autocorrelation function are obtained for different parameter ranges, and favorably compared to Monte Carlo simulations. Nonergodicity of the power spectrum of the process is briefly discussed, and a nonstationary Wiener-Khintchine theorem, relating the correlation functions and the power spectrum is presented. The considered situation is in full contrast to the usual assumptions of ergodicity and stationarity.

Key Words

NonergodicityTime seriesLévy statisticsPower lawCorrelation function

Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • Gennady Margolin
    • 1
  • Eli Barkai
    • 1
    • 2
  1. 1.Department of Chemistry and BiochemistryNotre Dame UniversityNotre Dame
  2. 2.Department of PhysicsBar Ilan UniversityRamat GanIsrael