Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Two-Pion Exchange NN-Potential in Nuclear Matter and Nuclear
  Stability   A meson exchange model of the $\pi\pi$ interaction which fits free $\pi\pi$
scattering data is used to calculate the interactions of pions in nuclear
matter as a function of nuclear density. Polarization of the nuclear medium by
the pions results in a marked increase in the s-wave $\pi\pi$ attraction at low
energy. The influence of this effect on the nucleon-nucleon interaction is a
corresponding increase with density of the $NN$ central potential due to the
exchange of two correlated pions, resulting in an $NN$ interaction which fails
to saturate. A possible mechanism for restoring the theoretical stability of
nuclear matter is explored and found to be effective.

13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph