Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isoscalar $\pi\pi$ scattering and the $\sigma$ meson resonance from QCD   We present for the first time a determination of the energy dependence of the
isoscalar $\pi\pi$ elastic scattering phase-shift within a first-principles
numerical lattice approach to QCD. Hadronic correlation functions are computed
including all required quark propagation diagrams, and from these the discrete
spectrum of states in the finite volume defined by the lattice boundary is
extracted. From the volume dependence of the spectrum we obtain the $S$-wave
phase-shift up to the $K\overline{K}$ threshold. Calculations are performed at
two values of the $u,d$ quark mass corresponding to $m_\pi = 236, 391$ MeV and
the resulting amplitudes are described in terms of a $\sigma$ meson which
evolves from a bound-state below $\pi\pi$ threshold at the heavier quark mass,
to a broad resonance at the lighter quark mass.

9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph