Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutron-Proton Correlations in an Exactly Solvable Model   We examine isovector and isoscalar neutron-proton correlations in an exactly
solvable model based on the algebra SO(8). We look particularly closely at
Gamow-Teller strength and double beta decay, both to isolate the effects of the
two kinds of pairing and to test two approximation schemes: the renormalized
neutron-proton QRPA (RQRPA) and generalized BCS theory. When isoscalar pairing
correlations become strong enough a phase transition occurs and the dependence
of the Gamow-Teller beta+ strength on isospin changes in a dramatic and
unfamiliar way, actually increasing as neutrons are added to an N=Z core.
Renormalization eliminates the well-known instabilities that plague the QRPA as
the phase transition is approached, but only by unnaturally suppressing the
isoscalar correlations. Generalized BCS theory, on the other hand, reproduces
the Gamow-Teller strength more accurately in the isoscalar phase than in the
usual isovector phase, even though its predictions for energies are equally
good everywhere. It also mixes T=0 and T=1 pairing, but only on the isoscalar
side of the phase transition.

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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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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: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph