Abstract

Single-file diffusion is a one-dimensional interacting infinite-particle system in which the order of particles never changes. An intriguing feature of single-file diffusion is that the mean-square displacement of a tagged particle exhibits an anomalously slow sub-diffusive growth. We study the full statistics of the displacement using a macroscopic fluctuation theory. For the simplest single-file system of impenetrable Brownian particles we compute the large deviation function and provide an independent verification using an exact solution based on the microscopic dynamics. For an arbitrary single-file system, we apply perturbation techniques and derive an explicit formula for the variance in terms of the transport coefficients. The same method also allows us to compute the fourth cumulant of the tagged particle displacement for the symmetric exclusion process.

Highlights

  • In non-equilibrium statistical mechanics, dynamical properties of interacting many-body systems play as important role as non-equilibrium steady states

  • The motion of an individual particle in a system of interacting particles is a fundamental dynamical problem in statistical mechanics even when the entire system is in equilibrium, or in a non-equilibrium steady state

  • We studied the full statistics of the displacement of the tagged particle in single-file diffusion

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Summary

Introduction

In non-equilibrium statistical mechanics, dynamical properties of interacting many-body systems play as important role as non-equilibrium steady states. The only solvable case corresponds to Brownian particles where D(ρ) = 1 and σ(ρ) = 2ρ For this single-file system we deduce a closed form formula for the cumulant generating function and the associated large deviation function. We verify the MFT predictions in the particular case of Brownian particles by comparing with exact results which we derive using the microscopic dynamics: the large deviation functions coming from these independent methods match perfectly. The variance in the annealed and quenched cases differ by 2 This was observed for the symmetric random average process [72] and for impenetrable Brownian particles [42], and it remains generally valid for single-file diffusion.

A hydrodynamic formulation
Variational formulation
Brownian particles with hard-core repulsion
Quenched case
Annealed case
Comparing annealed and quenched settings
Calculation of the variance for general single-file systems
The quenched initial state
The annealed initial state
The difference
Fourth cumulant of a tagged particle in the SEP
Probability of the tagged particle position
Comparison with a random field Ising model
Normal diffusion
Sub-diffusion
Summary
B Inequality between cumulants in the annealed and quenched cases
E Function G
Full Text
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