Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Faddeev Equation and Essential Spectrum of a Hamiltonian in Fock
  Space   A Hamiltonian (model operator) $H$ associated to a quantum system describing
three particles in interaction, without conservation of the number of
particles, is considered. The Faddeev type system of equations for eigenvectors
of $H$ is constructed. The essential spectrum of $H$ is described by the
spectrum of the channel operator.

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The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
31
The categories of this paper are: ao-sci