Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Virtual amplitudes and threshold behaviour of hadronic top-quark
  pair-production cross sections   We present the two-loop virtual amplitudes for the production of a top-quark
pair in gluon fusion. The evaluation method is based on a numerical solution of
differential equations for master integrals in function of the quark velocity
and scattering angle starting from a boundary at high-energy. The results are
given for the renormalized infrared finite remainders on a large grid and have
recently been used in the calculation of the total cross sections at the
next-to-next-to-leading order. For convenience, we also give the known results
for the quark annihilation case on the same grid. Outside of the kinematical
range covered by the grid, we provide threshold and high-energy expansions.
  From expansions of the two-loop virtual amplitudes, we determine the
threshold behavior of the total cross sections at next-to-next-to-leading order
for the quark annihilation and gluon fusion channels including previously
unknown constant terms. In our analysis of the quark annihilation channel, we
uncover the presence of a velocity enhanced logarithm of Coulombic origin,
which was missed in a previous study.

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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: math
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
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The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph