Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The crossover from single file to Fickian diffusion   The crossover from single-file diffusion, where the mean-square displacement
scales as <x^2> ~t^(1/2), to normal Fickian diffusion, where <x^2>~t$, is
studied as a function of channel width for colloidal particles.
  By comparing Brownian dynamics to a hybrid molecular dynamics and mesoscopic
simulation technique, we can study the effect of hydrodynamic interactions on
the single file mobility and on the crossover to Fickian diffusion for wider
channel widths. For disc-like particles with a steep interparticle repulsion,
the single file mobilities for different particle densities are well described
by the exactly solvable hard-rod model. This holds both for simulations that
include hydrodynamics, as well as for those that don't. When the single file
constraint is lifted, then for particles of diameter \sigma and pipe of width
$L$ such that (L- 2 \sigma)/\sigma = \delta_c << 1 the particles can be
described as hopping past one-another in an average time t_{hop}. For shorter
times t << t_{hop} the particles still exhibit sub-diffusive behaviour, but at
longer times t > t_{hop}, normal Fickian diffusion sets in with an effective
diffusion constant D_{hop} ~ t_{hop}^(1/2). For the Brownian particles, t_{hop}
~ 1/\delta_c^(2) when \delta << 1, but when hydrodynamic interactions are
included, we find a stronger dependence than \delta_c^{-2}. We attribute this
difference to short-range lubrication forces that make it more difficult for
particles to hop past each other in very narrow channels.

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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: gr-qc