Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical O(N) nonlinear sigma model on the half line: a study on
  consistent Hamiltonian description   The problem of consistent Hamiltonian structure for O(N) nonlinear sigma
model in the presence of five different types of boundary conditions is
considered in detail. For the case of Neumann, Dirichlet and the mixture of
these two types of boundaries, the consistent Poisson brackets are constructed
explicitly, which may be used, e.g. for the construction of current algebras in
the presence of boundary. While for the mixed boundary conditions and the
mixture of mixed and Dirichlet boundary conditions, we prove that there is no
consistent Poisson brackets, showing that the mixed boundary conditions are
incompatible with all nontrivial subgroups of $O((N)$.

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The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
9
The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con