Narrow Results

Based on a relativistic mean field (RMF) framework, we analyze the BCS approximation to the relativistic Hartree–Bogoliubov (RHB) approach for the case of nuclei close to the drip line. In the BCS calculations the single particle continuum corresponding to RMF is replaced by a set of discrete positive energy states generated by enclosing the nucleus in a box. It is found that the main contribution to the pairing correlations for the neutron-rich nuclei is given by the low-lying resonant states, in addition to the contributions coming from the states close to the Fermi surface. Towards this end we present the results of our calculations for the entire chain of even–even ^48–98Ni isotopes. Results for the neutron-rich nucleus ⁸⁴Ni is discussed in detail as a prototype. A detailed comparison of our results for the nucleus ⁸⁴Ni with those obtained in similar studies using RHB, nonrelativistic Hartree–Fock–Bogoliubov (HFB), and a recently proposed resonant continuum HF+BCS method provides strong evidence for the applicability of the RMF+BCS approach for the treatment of neutron-rich nuclei as well. Additional results of extensive calculations for the isotopes of O, Ca, Zr, Sn and Pb nuclei further reinforce our conclusions. From amongst these calculations, the results of the even–even ^32–76Ca isotopes with two different RMF force parametrizations, and their agreement with the recent continuum relativistic Hartree–Bogoliubov (CRHB) results are discussed briefly for illustration purposes.

We present a new non-parametric deprojection algorithm, DOPING (Deprojection of Observed Photometry using an INverse Gambit), which is designed to extract the three-dimensional luminosity density distribution ρ, from the observed surface brightness profile of an astrophysical system such as a galaxy or a galaxy cluster, in a generalised geometry, while taking into account changes in the intrinsic shape of the system. The observable is the 2D surface brightness distribution of the system. While the deprojection schemes presented hitherto have always worked within the limits of an assumed intrinsic geometry, in DOPING, geometry and inclination can be provided as inputs. The ρ that is most likely to project to the observed brightness data is sought; the maximisation of the likelihood is performed with the Metropolis algorithm. Unless the likelihood function is maximised, ρ is tweaked in shape and amplitude, while maintaining positivity, but otherwise the luminosity distribution is allowed to be completely free-form. Tests and applications of the algorithm are discussed.

Neutron and proton driplines of single-Λ and double-Λ hypernuclei, Ξ^- hypernuclei as well as normal nuclei are studied within a relativistic mean field approach using an extended form of the FSU Gold Lagrangian density. Hyperons are found to produce bound nuclei beyond the normal nuclear driplines. Radii are found to decrease in hypernuclei near the driplines, in line with observations in light Λ hypernuclei near the stability valley. The inclusion of a Ξ^- introduces a much larger change in radii than one or more Λ's.

In this paper, we study the binding energies, radii, single-particle energies, spin-orbit potential and density profile for multi-strange hypernuclei in the range of light mass to superheavy mass region within the relativistic mean field (RMF) theory. The stability of multi-strange hypernuclei as a function of introduced hyperons (Λ and Σ) is investigated. The neutron, lambda and sigma mean potentials are presented for light to superheavy hypernuclei. The inclusion of hyperons affects the nucleon, lambda and sigma spin-orbit potentials significantly. The bubble structure of nuclei and corresponding hypernuclei is studied. Nucleon and lambda halo structures are also investigated. A large class of bound multi-strange systems formed from the combination of nucleons and hyperons (n, p, Λ, Σ⁺ and n, p, Λ, Σ^-) is suggested in the region of superheavy hypernuclei which might be stable against the strong decay. These multi-strange systems might be produced in heavy-ion reactions.

We analyze the effects of δ–meson on hypernuclei within the framework of relativistic mean field theory. The δ–meson is included into the Lagrangian for hypernuclei. The extra nucleon–meson coupling (g_δ) affects every piece of physical observables, like binding energy, radii and single-particle energies of hypernuclei. Magnitude of effects in hypernuclei is found to be relatively less than their normal nuclei because of the presence of Λ hyperon. Flipping of single-particle energy levels are observed with the strength of g_δ in the considered hypernuclei as well as normal nuclei. The spin-orbit potentials are observed for considered hypernuclei and the effect of g_δ on spin-orbit potentials is also analyzed. The calculated Λ binding energy (B_Λ) are quite agreeable with experimental data. The sensitivity of B_Λ for s- and p- orbitals with the strength of g_δ is also analyzed. Lambda mean potential is investigated which is found to be consistent with other predictions.

The charge radii, the proton and neutron systems radii, as well as the matter radii of $N\approx Z$ odd-mass nuclei are studied using a particle-number projection approach in the neutron–proton (np) isovector ($T=1$) pairing case. Expressions of the proton and neutron systems quadratic radii are first established within a projection after variation method (i.e., of PBCS type) using a recently proposed wave function for odd-mass nuclei. It is checked that they reduce to the ones obtained in the like-particles pairing case. The new expressions are then used to study numerically the various radii of nuclei such as $16\le Z\le 48$ and $(N-Z)=1,3$, using the single-particle energies of a Woods–Saxon mean-field. It is shown that the few available experimental data are satisfactorily described by means of the present work approach. Furthermore, it appears that the np pairing and projection effects on the various radii are small on average in the case of odd-mass nuclei. However, the relative discrepancies with the values when only the pairing between like-particles is taken into account or the values obtained before the projection may reach up to 3% or 4% for some nuclei.