Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Meson Scattering in a Pion Superfluid   Instead of the fermion-fermion scattering which identifies the BCS-BEC
crossover in cold atom systems, boson-boson scattering is measurable and
characterizes the BCS-BEC crossover at quark level. We study $\pi$-$\pi$
scattering in a pion superfluid described by the Nambu--Jona-Lasinio model. We
found that the scattering amplitude drops down monotonically with decreasing
isospin density and finally vanishes at the boundary of the phase transition.
This indicates a BCS-BEC crossover in the pion superfluid.

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The categories of this paper are: mtrl-th
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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: astro-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc