Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metastability of a granular surface in a spinning bucket   The surface shape of a spinning bucket of granular material is studied using
a continuum model of surface flow developed by Bouchaud et al. and Mehta et al.
An experimentally observed central subcritical region is reproduced by the
model. The subcritical region occurs when a metastable surface becomes unstable
via a nonlinear instability mechanism. The nonlinear instability mechanism
destabilizes the surface in large systems while a linear instability mechanism
is relevant for smaller systems. The range of angles in which the granular
surface is metastable vanishes with increasing system size.

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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph