dorsal/arxiv
View SchemaNeutron-Proton Correlations in an Exactly Solvable Model
| Authors | J. Engel, S. Pittel, P. Vogel, M. Stoitsov, J. Dukelsky |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9610045 |
| URL | https://arxiv.org/abs/nucl-th/9610045 |
| DOI | 10.1103/PhysRevC.55.1781 |
| Journal | Phys.Rev.C55:1781-1788,1997 |
Abstract
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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"abstract": "We examine isovector and isoscalar neutron-proton correlations in an exactly\nsolvable model based on the algebra SO(8). We look particularly closely at\nGamow-Teller strength and double beta decay, both to isolate the effects of the\ntwo kinds of pairing and to test two approximation schemes: the renormalized\nneutron-proton QRPA (RQRPA) and generalized BCS theory. When isoscalar pairing\ncorrelations become strong enough a phase transition occurs and the dependence\nof the Gamow-Teller beta+ strength on isospin changes in a dramatic and\nunfamiliar way, actually increasing as neutrons are added to an N=Z core.\nRenormalization eliminates the well-known instabilities that plague the QRPA as\nthe phase transition is approached, but only by unnaturally suppressing the\nisoscalar correlations. Generalized BCS theory, on the other hand, reproduces\nthe Gamow-Teller strength more accurately in the isoscalar phase than in the\nusual isovector phase, even though its predictions for energies are equally\ngood everywhere. It also mixes T=0 and T=1 pairing, but only on the isoscalar\nside of the phase transition.",
"arxiv_id": "nucl-th/9610045",
"authors": [
"J. Engel",
"S. Pittel",
"P. Vogel",
"M. Stoitsov",
"J. Dukelsky"
],
"categories": [
"nucl-th"
],
"doi": "10.1103/PhysRevC.55.1781",
"journal_ref": "Phys.Rev.C55:1781-1788,1997",
"title": "Neutron-Proton Correlations in an Exactly Solvable Model",
"url": "https://arxiv.org/abs/nucl-th/9610045"
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