Competition of isoscalar and isovector proton-neutron pairing in nuclei
Abstract We use shell model techniques in the complete pf shell to study pair correlations in nuclei. Particular attention is paid to the competition of isoscalar and isovector proton-neutron pairing modes which is investigated in the odd-odd N = Z nucleus 46 V and in the chain of even Fe-isotopes. We confirm the dominance of isovector pairing in the ground states. An inspection of the level density and pair correlation strength in 46 V, however, shows the increasing relative importance of isoscalar correlations with increasing excitation energy. In the Fe-isotopes we find the expected strong dependence of the proton-neutron isovector pairing strength on the neutron excess, while the dominant J = 1 isoscalar pair correlations scale much more gently with neutron number. We demonstrate that the isoscalar pair correlations depend strongly on the spin-orbit splitting.
Practical solution to the Monte Carlo sign problem: Realistic calculations of 54Fe.
We present a practical solution to the "sign problem" in the auxiliary field Monte Carlo approach to the nuclear shell model. The method is based on extrapolation from a continuous family of problem-free Hamiltonians. To demonstrate the resultant ability to treat large shell-model problems, we present results for the 54Fe in the full fp-shell basis using the Brown-Richter interaction. We find the Gamow-Teller β+ strength to be quenched by 58% relative to the single-particle estimate, in better agreement with experiment than previous estimates based on truncated bases.
The Vector Coherent State Method and Its Application to Problems of Higher Symmetries
1. Introduction.- 2. The vector coherent state method.- 3. Detailed examples.- 4. Other applications.- 5. The calculation of SU(3) Wigner coefficients.- 6. An indirect application of vector coherent state theory: Construction of a group theoretically sound orthonormal Wigner supermultiplet basis.