Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solutions of the Differential Inequality with a~Null Lagrangian:
  Regularity and Removability of Singularities   We prove a theorem on self-improving regularity for derivatives of solutions
of the inequality $F(v'(x))\le KG(v'(x))$ constructed by means of a quasiconvex
function $F$ and a null Lagrangian $G$. We apply this theorem to improve the
stability and H\"older regularity results of \cite{Egor2008} and to establish a
theorem on removability of singularities for solutions of this inequality.

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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: nlin