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Pairing and continuum effects in nuclei close to the drip line  [PDF]
M. Grasso,N. Sandulescu,Nguyen Van Giai,R. J. Liotta
Physics , 2001, DOI: 10.1103/PhysRevC.64.064321
Abstract: The Hartree-Fock-Bogoliubov (HFB) equations in coordinate representation are solved exactly, i.e., with correct asymptotic boundary conditions for the continuous spectrum. The calculations are preformed with effective Skyrme interactions. The exact HFB solutions are compared with HFB calculations based on box boundary conditions and with resonant continuum Hartree-Fock-BCS (HF-BCS) results. The comparison is done for the neutron-rich Ni isotopes. It is shown that close to the drip line the amount of pairing correlations depends on how the continuum coupling is treated. On the other hand, the resonant continuum HF-BCS results are generally close to those of HFB even in neutron-rich nuclei.
Quasi-particle continuum and resonances in the Hartree-Fock-Bogoliubov theory  [PDF]
J. C. Pei,A. T. Kruppa,W. Nazarewicz
Physics , 2011, DOI: 10.1103/PhysRevC.84.024311
Abstract: The quasi-particle energy spectrum of the Hartree-Fock-Bogoliubov (HFB) equations contains discrete bound states, resonances, and non-resonant continuum states. We study the structure of the unbound quasi-particle spectrum of weakly bound nuclei within several methods that do not rely on imposing scattering or outgoing boundary conditions. Various approximations are examined to estimate resonance widths. It is shown that the stabilization method works well for all HFB resonances except for very narrow ones. The Thomas-Fermi approximation to the non-resonant continuum has been shown to be very effective, especially for coordinate-space HFB calculations in large boxes that involve huge amounts of discretized quasi-particle continuum states.
Pair correlation of giant halo nuclei in continuum Skyrme-Hartree-Fock-Bogoliubov theory  [PDF]
Y. Zhang,M. Matsuo,J. Meng
Physics , 2012, DOI: 10.1103/PhysRevC.86.054318
Abstract: The giant halos predicted in neutron-rich Zr isotopes with $A=124-138$ are investigated by using the self-consistent continuum Skyrme Hartree-Fock-Bogoliubov approach, in which the asymptotic behavior of continuum quasiparticle states is properly treated by the Green's function method. We study in detail the neutron pair correlation involved in the giant halo by analyzing the asymptotic exponential tail of the neutron pair condensate (pair density) in addition to that of the neutron particle density. The neutron quasiparticle spectra associated with these giant halo nuclei are examined. It is found that the asymptotic exponential tail of the neutron pair condensate is dominated by non-resonant continuum quasiparticle states corresponding to the scattering states with low asymptotic kinetic energy. This is in contrast to the asymptotic tail of the neutron density, whose main contributions arise from the resonant quasiparticle states corresponding to the weakly-bound single-particle orbits and resonance orbits in the Hartree-Fock potential.
Hartree-Fock+BCS approach to unstable nuclei with the Skyrme force  [PDF]
Naoki Tajima
Physics , 2003, DOI: 10.1143/PTPS.142.265
Abstract: We reanalyze the results of our extensive Hartree-Fock + BCS calculation from new points of view paying attention to the properties of unstable nuclei. The calculation has been done with the Skyrme SIII force for the ground and shape isomeric states of 1029 even-even nuclei ranging 2 <= Z <= 114. We also discuss the advantages of the employed three-dimensional Cartesian-mesh representation, especially on its remarkably high precision with apparently coarse meshes when applied to atomic nuclei. In Appendices we give the coefficients of finite-point numerical differentiation and integration formulae suitable for Cartesian mesh representation and elucidate the features of each formula and the differences from a method based on the Fourier transformation.
Extensive Hartree-Fock + BCS calculation with Skyrme SIII force  [PDF]
Naoki Tajima,Satoshi Takahara,Naoki Onishi
Physics , 1996, DOI: 10.1016/0375-9474(96)00156-X
Abstract: We have performed deformed Hartree-Fock+BCS calculations with the Skyrme SIII force for the ground states of even-even nuclei with 2 <= Z <= 114 and N ranging from outside the proton drip line to beyond the experimental frontier in the neutron-rich side. We obtained spatially localized solutions for 1029 nuclei, together with the second minima for 758 nuclei. The single-particle wavefunctions are expressed in a three-dimensional Cartesian-mesh representation, which is suitable to describe nucleon skins, halos, and exotic shapes as well as properties of ordinary stable nuclei. After explaining some of the practical procedures of the calculations, we compare the resulting nuclear masses with experimental data and the predictions of other models. We also discuss the quadrupole (m=0, 2) and hexadecapole (m=0, 2, 4) deformations, the skin thicknesses, the halo radii, and the energy difference between the oblate and the prolate solutions. Our results can be obtained via computer network.
Calculation of direct-semidirect radiative proton capture with Skyrme-Hartree-Fock-BCS model  [cached]
Watanabe T.,Kawano T.,Bonneau L.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100209002
Abstract: We calculate the direct-semidirect (DSD) radiative proton capture cross section on 112Sn, 63Cu, and 209Bi in the microscopic Hartree-Fock-BCS approach using the Skyrme interaction. Compared to the compound process, the DSD process becomes dominant in the proton capture reaction above ten and several MeV incident proton energies. We compare several particle-vibration coupling forms, which is sensitive to the semidirect cross section.
E(5) and X(5) shape phase transitions within a Skyrme Hartree-Fock + BCS approach  [PDF]
R. Rodriguez-Guzman,P. Sarriguren
Physics , 2007, DOI: 10.1103/PhysRevC.76.064303
Abstract: Self-consistent Skyrme Hartree-Fock plus BCS calculations are performed to generate potential energy curves (PEC) in various chains of Pd, Xe, Ba, Nd, Sm, Gd, and Dy isotopes. The evolution of shapes with the number of nucleons is studied in a search for signatures of E(5) and X(5) critical point symmetries. It is shown that the energy barriers in the PECs are determined to a large extent by the treatment of the pairing correlations.
Quantum quenches and competing orders: I. Time-dependent Hartree-Fock+BCS theory  [PDF]
Wenbo Fu,Ling-Yan Hung,Subir Sachdev
Physics , 2014, DOI: 10.1103/PhysRevB.90.024506
Abstract: We study the non-equlibrium dynamics of an electronic model of competing bond density wave order and $d$-wave superconductivity. In a time-dependent Hartree-Fock+BCS approximation, the dynamics reduces to the equations of motion of operators realizing the generators of SU(4) at each pair of momenta, $(\boldsymbol{k}, -\boldsymbol{k})$, in the Brillouin zone. We compare the results of numerical studies of our model with recent picosecond optical experiments.
Gamow-Hartree-Fock-Bogoliubov Method: Representation of quasiparticles with Berggren sets of wave functions  [PDF]
N. Michel,K. Matsuyanagi,M. Stoitsov
Physics , 2008, DOI: 10.1103/PhysRevC.78.044319
Abstract: Single-particle resonant states, also called Gamow states, as well as bound and scattering states of complex energy form a complete set, the Berggren completeness relation. It is the building block of the recently introduced Gamow Shell Model, where weakly bound and resonant nuclear wave functions are expanded with a many-body basis of Slater Determinants generated by this set of single-particle states. However, Gamow states have never been studied in the context of Hartree-Fock-Bogoliubov theory, except in the Bardeen-Cooper-Schriefer (BCS) approximation, where both the upper and lower components of a quasiparticle wave function are assumed to possess the same radial dependence with that of a Gamow state associated with the Hartree-Fock potential. Hence, an extension of the notion of Gamow state has to be effected in the domain of quasiparticles. It is shown theoretically and numerically that bound, resonant and scattering quasiparticles are well defined and form a complete set, by which bound Hartree-Fock-Bogoliubov ground states can be constructed. It is also shown that the Gamow-Hartree-Fock single-particle basis can be used to solve the Gamow-Hartree-Fock-Bogoliubov problem. As an illustration, the proposed method is applied to neutron-rich Nickel isotopes close to the neutron drip-line.
Continuum quasiparticle random phase approximation and the time dependent Hartree-Fock-Bogoliubov approach  [PDF]
E. Khan,N. Sandulescu,M. Grasso,Nguyen Van Giai
Physics , 2002, DOI: 10.1103/PhysRevC.66.024309
Abstract: Quadrupole excitations of neutron-rich nuclei are analyzed by using the linear response method in the Quasiparticle Random Phase Approximation (QRPA). The QRPA response is derived starting from the time-dependent Hartree-Fock-Bogoliubov (HFB) equations. The residual interaction between the quasiparticles is determined consistently from the two-body force used in the HFB equations, and the continuum coupling is treated exactly. Calculations are done for the neutron-rich oxygen isotopes. It is found that pairing correlations affect the low-lying states, and that a full treatment of the continuum can change the structure of the states in the giant resonance region.
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