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Centre-of-mass like superposition of Ornstein–Uhlenbeck processes: A pathway to non-autonomous stochastic differential equations and to fractional diffusion

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Published/Copyright: January 13, 2019

Abstract

We consider an ensemble of Ornstein–Uhlenbeck processes featuring a population of relaxation times and a population of noise amplitudes that characterize the heterogeneity of the ensemble. We show that the centre-of-mass like variable corresponding to this ensemble is statistically equivalent to a process driven by a non-autonomous stochastic differential equation with time-dependent drift and a white noise. In particular, the time scaling and the density function of such variable are driven by the population of timescales and of noise amplitudes, respectively. Moreover, we show that this variable is equivalent in distribution to a randomly-scaled Gaussian process, i.e., a process built by the product of a Gaussian process times a non-negative independent random variable. This last result establishes a connection with the so-called generalized grey Brownian motion and suggests application to model fractional anomalous diffusion in biological systems.

Acknowledgements

This research is supported by the Basque Government through the BERC 2014-2017 and the BERC 2018-2021 programs, and by the Spanish Ministry of Economy and Competitiveness MINECO through BCAM Severo Ochoa excellence accreditation SEV-2013-0323 and through project MTM2016-76016-R “MIP”. VS acknowledges BCAM for the financial support to her internship research period, and SV acknowledges the University of Bologna for the financial support through the “Marco Polo Programme” for funding her PhD research period abroad spent at BCAM.

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Received: 2018-02-03
Published Online: 2019-01-13
Published in Print: 2018-10-25

© 2018 Diogenes Co., Sofia

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