• Accepted Paper

Mean-field theory of myopic self-avoiding fractional Brownian motion

Rashad Bakhshizada, Skirmantas Janušonis, Ralf Metzler, and Thomas Vojta

Phys. Rev. E - Accepted 5 November, 2026

DOI: https://doi.org/10.1103/h4tz-8bmt

Abstract

Myopic self-avoiding fractional Brownian motion (FBM) is a stochastic process in which an ensemble of particles is driven by fractional Gaussian noise while being repelled by the gradient of the time-integrated ensemble density [J. House, R. Bakhshizada, S. Janusonis, R. Metzler, and T. Vojta, Phys. Rev. E 112, 034119 (2025)]. Depending on the anomalous diffusion exponent α characterizing the noise, the process features two dynamical regimes: an interaction-dominated regime (α < α_c = 4/(d + 2)) where the mean-density interaction governs long-time dynamics, and a noise-dominated regime (α > αc) where FBM correlations prevail. In the interaction-dominated regime, the mean-squared displacement grows as ⟨r^2(t)⟩ ∼ t^(4/(d+2)) regardless of α, while for α > α_c the standard FBM scaling ⟨r^2(t)⟩ ∼ t^α is recovered. Here, we develop an analytical mean-field theory of myopic self-avoiding FBM, based on a Fokker-Planck approach to the interaction-dominated regime. This allows us to derive closed-form polynomial solutions for the probability density. To compare with computer simulations, we develop an efficient radial binning algorithm that significantly reduces the computational complexity, making large-scale three-dimensional simulations feasible. Extensive simulations in one, two, and three dimensions confirm the analytical predictions. We also discuss the application of the process to the self-organization of serotonergic axons (fibers) in vertebrate brains, where FBM paths with self-avoidance provide a natural framework for understanding spatial heterogeneities of fiber densities.

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