Nuclear Theory·nucl-th

Wednesday·November 6, 2024

6 papers—3 primary·3 cross-listed

01
[Submitted on 5 Nov 2024]
Rotating Neutron Stars with the Relativistic Ab Initio Calculations
Xiaoying Qu · Sibo Wang · Hui Tong
The equation of state (EOS) of extremely dense matter is crucial for understanding the properties of rotating neutron stars. Starting from the widely used realistic Bonn potentials rooted in a relativistic framework, we derive EOSs by performing the state-of-the-art relativistic Brueckner-Hartree-Fock (RBHF) calculations in the full Dirac space. The self-consistent and simultaneous consideration of both positive- and negative-energy states (NESs) of the Dirac equation allows us to avoid the uncertainties present in calculations where NESs are treated using approximations. To manifest the impact of rotational dynamics, several structural properties of neutron stars across a wide range of rotation frequencies and up to the Keplerian limit are obtained, including the gravitational and baryonic masses, the polar and equatorial radii, and the moments of inertia. Our theoretical predictions align well with the latest astrophysical constraints from the observations on massive neutron stars and joint mass-radius measurements. The maximum mass for rotating configurations can reach up to $2.93 M_{⊙}$ for Bonn A potential, while the radius of a $1.4 M_{⊙}$ neutron star for non-rotating case can be extended to around 17 km through the constant baryonic mass sequences. Relations with good universalities between the Keplerian frequency and static mass as well as radius are obtained, from which the radius of the black widow PSR J0952-0607 is predicted to be less than 19.58 km. Furthermore, to understand how rotation deforms the equilibrium shape of a neutron star, the eccentricity is also calculated. The approximate universality between the eccentricity at the Keplerian frequency and the gravitational mass is found.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.02878 [pdf]
ApJ(2025)·6 citations
02
[Submitted on 5 Nov 2024]
Tetrahedral shape and Lambda impurity effect in $^{80}$ Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model
Dan Yang🇨🇳 · Yu-Ting Rong🇨🇳
This study investigates the tetrahedral structure in $^{80}$ Zr and Lambda ( $Λ$ ) impurity effect in $_{Λ}^{81}$ Zr using the multidimensionally constrained relativistic Hartree-Bogoliubov model. The ground states of both $^{80}$ Zr and $_{Λ}^{81}$ Zr exhibit a tetrahedral configuration, accompanied by prolate and axial-octupole shape isomers. Our calculations reveal there are changes in the deformation parameters $β_{20}$ , $β_{30}$ , and $β_{32}$ upon $Λ$ binding to $^{80}$ Zr, except for $β_{32}$ when $Λ$ occupies $p$ -orbits. Compared to the two shape isomers, the $Λ$ particle exhibits weaker binding energy in the tetrahedral state when occupying the $1/ 2^{+} [000] (Λ_{s})$ or $1/ 2^{-} [110]$ single-particle states. In contrast, the strongest binding occurs for the $Λ$ particle in the $1/ 2^{-} [101]$ state with tetrahedral shape. Besides, a large $Λ$ separation energy may not necessarily correlate with a significant overlap between the density distributions of the $Λ$ particle and the nuclear core, particularly for tetrahedral hypernuclei.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.02946 [pdf]
CPC(2025)·1 citation
03
[Submitted on 5 Nov 2024]
Potential signature of new magicity from universal aspects of nuclear charge radii
Dan Yang · Yu-Ting Rong · Rong An · Rui-Xiang Shi
Shell quenching phenomena in nuclear charge radii are typically observed at the well-established neutron magic numbers. However, the recent discovery of potential new magic numbers at the neutron numbers $N = 32$ and $N = 34$ has sparked renewed interest in this mass region. This work further inspects into the charge radii of nuclei around the $N = 28$ shell closure using the relativistic Hartree-Bogoliubov model. We incorporate meson exchange and point-coupling effective nucleon-nucleon interactions alongside the Bogoliubov transformation for pairing corrections. To accurately capture the odd-even staggering and shell closure effects observed in charge radii, neutron-proton correlations around Fermi surface are explicitly considered. The charge radii of Ca and Ni isotopes are used to test the theoretical model and show an improvement with neutron-proton pairing corrections, in particular for neutron-rich isotopes. Our calculations reveal a inverted parabolic-like trend in the charge radii along the $N = 28$ isotones for proton numbers $Z$ between 20 and 28. Additionally, the shell closure effect of $Z = 28$ persists across the $N = 28$ , 30, 32, and 34 isotonic chains, albeit with a gradual weakening trend. Notably, the significantly abrupt changes in charge radii are observed across $Z = 22$ along both the $N = 32$ and $N = 34$ isotonic chains. This kink at $Z = 22$ comes from the sudden decrease of the neuron-proton correlation around Fermi surfaces across $Z = 22$ for $N = 30$ , 32, and 34 isotones, and might provide a signature for identifying the emergence of neutron magic numbers $N = 32$ and 34. Furthermore, the calculated charge radii for these isotonic chains ( $N = 28$ , 30, 32, and 34) can serve as reliable guidelines for future experimental measurements.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.03076 [pdf]
PRC(2024)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Rotating Neutron Stars with the Relativistic Ab Initio Calculations

Tetrahedral shape and Lambda impurity effect in 80Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model

Potential signature of new magicity from universal aspects of nuclear charge radii

Affiliations

Tetrahedral shape and Lambda impurity effect in $^{80}$ Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model