Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pre-avalanche instabilities in a granular pile   We investigate numerically the transition between static equilibrium and
dynamic surface flow of a 2D cohesionless granular system driven by a
continuous gravity loading. This transition is characterized by intermittent
local dynamic rearrangements and can be described by an order parameter defined
as the density of critical contacts, e.g. contacts where the friction is fully
mobilized. Analysis of the spatial correlations of critical contacts shows the
occurence of ``fluidized'' clusters which exhibit a power-law divergence in
size at the approach of the stability limit. The results are compatible with
recent models that describe the granular system during the static/dynamic
transition as a multi-phase system.

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The categories of this paper are: dg-ga
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph