Relativistic Mean-field Effective Interaction Research Articles

Iron group nuclei electron capture in super-Chandrasekhar superstrong magnetic white dwarfs

Using the theory of relativistic mean-field effective interactions, the influences of superstrong magnetic fields (SMFs) on electron Fermi energy, binding energy per nucleus and single-particle level structure are discussed in super-Chandrasekhar magnetic white dwarfs. Based on the relativistical SMFs theory model of Potekhin et al., the electron chemical potential is corrected in SMFs, and the electron capture (EC) of iron group nuclei is investigated by using the Shell-Model Monte Carlo method and Random Phase Approximation theory. The EC rates can increase by more than three orders of magnitude due to the increase of the electron Fermi energy and the change of single-particle level structure by SMFs. However, the EC rates can decrease by more than four orders of magnitude due to increase of the nuclei binding energy by SMFs. We compare our results with those of FFNs (Fuller et al.), AUFDs (Aufderheide et al.) and Nabi (Nabi et al.). Our rates are higher by about four orders of magnitude than those of FFN, AUFD and Nabi due to SMFs. Our study may have important reference value for subsequent studies of the instability, mass radius relationship, and thermal and magnetic evolution of super-Chandrasekhar magnetic white dwarfs.

Instability Due to Electron Captures of Nuclei 56Ni, 56Co, 56Fe, 56Mn, 56Cr, and 56V in Strongly Magnetized Super-Chandrasekhar White Dwarfs

Based on the theory of the relativistic mean-field effective interactions, we explore the effect of superstrong magnetic fields (SMFs) on nuclear single-particle level structure, nuclear blinding energy, and the electron Fermi energy in strongly magnetized super-Chandrasekhar white dwarfs (SMSWDs). We also discuss the electron capture (EC) instability from the threshold mass density (TMD) and threshold pressure (TP) for some typical iron group nuclei in SMSWD due to SMFs. At relatively low densities (e.g., ρ 7 = 57, 97, 197), the EC rates increase and they then decrease by more than four orders of magnitude. However, at relatively higher density (e.g., ρ 7 = 4197), the rates increase by about two orders of magnitude when 2 × 103 < B 12 < 5 × 104, and then the SMFs have a minor effect on EC rates. The TMD (TP) can increase by about 23% ∼ 29%, due to an increase in the electron–ion interaction and nuclear binding energy in SMFs. As SMFs further increase, the TMD (TP) increase almost linearly for one Landau levels system. For a two and three Landau level system, the SMFs have a slight influence on the TMD (TP) (e.g., at B 12 = 103.5), and then TMD (TP) increases by about 13% ∼ 14%, and finally decreases by about 27.85% (27.34%). The shift of the onset of EC can make the maximum mass of the SMSWD increase by more than 2.28% for a one Landau level system. This influence from TMD (TP) can be larger than that of general relativity for SMSWD, which contains some iron group nuclei.

Relativistic Hartree Bogoliubov model with Density Dependent meson-nucleon couplings

A new improved relativistic mean-field effective interaction with explicit density dependence of the meson-nucleon couplings is proposed. The new effective interaction is called DD-ME2 and it is tested in Relativistic Hartree-Bogoliubov (RHB) and RPA calculations of nuclear ground-states and properties of excited states.

Magnetar crust electron capture for ^{55}Co and ^{56}Ni

Based on the relativistic mean-field effective interaction principle and random phase approximation theory in superstrong magnetic fields (SMFs), we present an analysis of the influence of SMFs on the electron Fermi energy, nuclear blinding energy, single-particle level structure and electron capture for ^{55}Co, and ^{56}Ni by the shell-model Monte Carlo method in the magnetar’s crust. The electron capture rates increase by two orders of magnitude due to an increase in the electron Fermi energy and a change in single-particle level structure by SMFs. Then the rates decrease by more than two orders of magnitude due to an increase in the nuclear binding energy and a reduction in the electron Fermi energy by SMFs.

A NEW INSIGHT INTO NEUTRINO ENERGY LOSS BY ELECTRON CAPTURE OF IRON GROUP NUCLEI IN MAGNETAR SURFACES

ABSTRACT Based on the relativistic mean-field effective interactions theory, and the Lai dong model, we discuss the influences of superstrong magnetic fields (SMFs) on electron Fermi energy, nuclear blinding energy, and single-particle level structure in magnetar surfaces. Using the Shell-Model Monte Carlo method and the Random Phase Approximation theory, we analyze the neutrino energy loss rates (NELRs) by electron capture for iron group nuclei in SMFs. First, when B 12 &lt; 100, we find that the SMFs have a slight influence on the NELRs for most nuclides at relativistic low temperatures (e.g., T 9 = 0.233); nevertheless, the NELRs increase by more than four orders of magnitude at relativistic high temperatures (e.g., T 9 = 15.53). When B 12 &gt; 100, the NELRs decrease by more than three orders of magnitude (e.g., at T 9 = 15.53 for 52–61Fe, 55–60Co, and 56–63Ni). Second, for a certain value of magnetic field and temperature, the NELRs increase by more than four orders of magnitude when , but as the density increases (i.e., when ), there is almost no influence on the density of NELRs. For the density around , there is an abrupt increase in NELRs when B 12 ≥ 103.5. Such jumps are an indication that the underlying shell structure has changed due to single-particle behavior by SMFs. Finally, we compare our NELRs with those of Fuller et al. (FFN) and Nabi &amp; Klapdor-Kleingrothaus (NKK). For the case without SMFs, one finds that our rates for certain nuclei are close to about five orders of magnitude lower than FFN and NKK at relativistic low temperatures (e.g., T 9 = 1). However, at a relativistic high temperature (e.g., T 9 = 3), our results are in good agreement with NKK, but about one order of magnitude lower than FFN. For the case with SMFs, our NELRs for some iron group nuclei can be about five orders of magnitude higher than those of FFN and NKK. (Note that B 12, T 9, and ρ 7 are in units of 1012 G, 109 K, and , respectively.)

PAIRING PROPERTIES OF SYMMETRIC NUCLEAR MATTER IN RELATIVISTIC MEAN FIELD THEORY

The properties of pairing correlations in symmetric nuclear matter are studied in the relativistic mean field (RMF) theory with the effective interaction, PK1. Considering the well-known problem that the pairing gap at the Fermi surface calculated with RMF effective interactions is three times larger than that with the Gogny force, an effective factor in the particle–particle channel is introduced. For the RMF calculation with PK1, an effective factor of 0.76 gives a maximum pairing gap of 3.2 MeV at a Fermi momentum of 0.9 fm-1, which is consistent with the result with the Gogny force.

New relativistic mean-field interaction with density-dependent meson-nucleon couplings

We adjust a new improved relativistic mean-field effective interaction with explicit density dependence of the meson-nucleon couplings. The effective interaction DD-ME2 is tested in relativistic Hartree-Bogoliubov and quasiparticle random-phase approximation (QRPA) calculations of nuclear ground states and properties of excited states, in calculation of masses, and it is applied to the analysis of very recent data on superheavy nuclei.

Ground-state properties of rare-earth nuclei in the relativistic Hartree-Bogoliubov model with density-dependent meson-nucleon couplings

The relativistic mean-field effective interaction with density-dependent meson-nucleon couplings DD-ME1 is tested in the calculation of deformed nuclei. Ground-state properties of six isotopic chains ($60\le Z \le 70$) in the region of rare-earth nuclei are calculated by using the relativistic Hartree-Bogoliubov (RHB) model with the DD-ME1 mean-field interaction, and with the Gogny D1S force for the pairing interaction. Results of fully self-consistent RHB calculations for the total binding energies, charge isotope shifts and quadrupole deformation parameters are compared with the available empirical data.

Relativistic Hartree-Bogoliubov and QRPA description of exotic nuclear structure

The relativistic Hartree-Bogoliubov (RHB) model is extended to include density-dependent meson-nucleon vertex functions. Compared with standard relativistic mean-field effective interactions with non-linear meson-exchange terms, the density-dependent meson-nucleon couplings provide an improved description of asymmetric nuclear matter, neutron matter and nuclei far from stability. The relativistic quasiparticle random-phase approximation (RQRPA) is formulated in the canonical single-nucleon basis of the relativistic Hartree-Bogoliubov (RHB) model. Both in the particle-hole and particle-particle channels, the same interactions are used in the RHB calculation of the ground state and in the matrix equations of the RQRPA. The RHB + RQRPA is employed in the analysis of multipole excitations of neutron-rich oxygen isotopes.

Shape coexistence in the relativistic Hartree-Bogoliubov approach

The phenomenon of shape coexistence is studied in the relativistic Hartree-Bogoliubov framework. Standard relativistic mean-field effective interactions do not reproduce the ground-state properties of neutron-deficient Pt-Hg-Pb isotopes. It is shown that, in order to consistently describe binding energies, radii, and ground-state deformations of these nuclei, effective interactions have to be constructed, which take into account the sizes of spherical shell gaps.

Finite-nuclei calculations based on relativistic mean-field effective interactions

The Dirac-Brueckner-Hartree-Fock calculations of nuclear matter are parametrized by the relativistic σω mean-field theory with scalar and vector nonlinear self-interactions. The effective interactions thus obtained are used in the relativistic mean-field studies of the structure of 16 O and 40 Ca nuclei without the introduction of additional free parameters. The calculated binding energies, single-particle spectra and charge radii agree quite well (although not satisfactorily) with experimental data and present an improvement over the nonrelativistic Brueckner-Hartree-Fock approximations.