Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Integrable S-matrices, massive and massless modes and the AdS_2 x S^2
  superstring   We derive the exact S-matrix for the scattering of particular representations
of the centrally-extended psu(1|1)^2 Lie superalgebra, conjectured to be
related to the massive modes of the light-cone gauge string theory on AdS_2 x
S^2 x T^6. The S-matrix consists of two copies of a centrally-extended psu(1|1)
invariant S-matrix and is in agreement with the tree-level result following
from perturbation theory. Although the overall factor is left unfixed, the
constraints following from crossing symmetry and unitarity are given. The
scattering involves long representations of the symmetry algebra, and the
relevant representation theory is studied in detail. We also discuss Yangian
symmetry and find it has a standard form for a particular limit of the
aforementioned representations. This has a natural interpretation as the
massless limit, and we investigate the corresponding limits of the massive
S-matrix. Under the assumption that the massless modes of the light-cone gauge
string theory transform in these limiting representations, the resulting
S-matrices would provide the building blocks for the full S-matrix. Finally,
some brief comments are given on the Bethe ansatz.

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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph