Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Boundary problems for three-dimensional Dirac operators and generalized
  MIT bag models for unbounded domains   We consider operators of boundary value problems for 3D- Dirac operators in
unbounded domains with the uniformly regular boundary. We give effective
conditions of self-adjointness of operators under consideration and a
description of their essential spectra. We also give applications to operators
of the MIT bag problems for unbounded domains

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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: stat
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg