Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The ChPT: top-down and bottom-up   In this work, higher-derivative corrections of the non-linear sigma model of
both even and odd intrinsic-parity sectors are systematically studied, focusing
on ordered amplitudes of flavor scalars in massless limit. It should correspond
to a theory known as Chiral perturbation theory (ChPT) without external sources
and with only single-trace operators. We briefly overview its formal
development and apply new S-matrix methods to its amplitude constructions. The
bottom-up analysis of the tree-level amplitudes of different orders and
multiplicities focuses on the formal structure of general ChPT. Possible
theoretical simplifications based on the Kleiss-Kuijf and
Bern-Carrasco-Johansson relations are presented. Finally, in the same context,
the comparison with the so-called Z-function, which is connected with string
theory, is also discussed.

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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn