Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Higher-order tree-level amplitudes in the nonlinear sigma model   We present a generalisation of the flavour-ordering method applied to the
chiral nonlinear sigma model with any number of flavours. We use an extended
Lagrangian with terms containing any number of derivatives, organised in a
power-counting hierarchy. The method allows diagrammatic computations at
tree-level with any number of legs at any order in the power-counting. Using an
automated implementation of the method, we calculate amplitudes ranging from 12
legs at leading order, $\mathcal{O}(p^2)$, to 6 legs at
next-to-next-to-next-to-leading order, $\mathcal{O}(p^8)$. In addition to this,
we generalise several properties of amplitudes in the nonlinear sigma model to
higher orders. These include the double soft limit and the uniqueness of
stripped amplitudes.

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The categories of this paper are: stat
29
The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys