Speaker
Nicolae Sandulescu
Description
The common treatment of proton-neutron pairing in N ≅ Z
nuclei relies on Cooper pairs and mean-field BCS-type
models. However, the nuclear interaction can induce, through
the isospin conservation, quartet correlations of alpha type
which might compete with the Cooper pairs. In fact, for any
isovector pairing interactions the ground state of N=Z
systems is accurately described not by Cooper pairs but in
terms of collective quartets [1,2]. Cooper pairs and
quartets can however coexist in isospin asymmetric systems
with N>Z. In this case the ground state of the isovector
pairing Hamiltonian can be described with high precision as
a condensate of alpha-like quartets to which it is appended
a condensate of Cooper pairs built with the excess neutrons
[3,4]. Quartets appear to be the relevant degrees of
freedom for treating not only the isovector pairing but also
the competition between the isoscalar and the isovector
proton-neutron pairing in N=Z nuclei [5]. These facts
indicate that the many-body pairing problem in N ≅ Z nuclei
can be more efficiently treated in calculation schemes based
on alpha-type quartets rather than on Cooper pairs and
BCS-type models.
1.N. Sandulescu, D. Negrea, J. Dukelski, C. W. Johnson,
Phys. Rev. C85, 061303 (R) (2012); 2. N. Sandulescu, D.
Negrea, C. W. Johnson, Phys. Rev. C86, 041302 (R) (2012); 3.
M. Sambataro and N. Sandulescu, Phys Rev. C88, 061303
(R)(2013) ; 4. D. Negrea and N. Sandulescu, Phys. Rev. C
(2014), in press; 5. M. Sambataro, N. Sandulescu and C. W.
Johnson, in preparation
