Nuclear Theory·nucl-th

Wednesday·October 20, 2021

3 papers—2 primary·1 cross-listed

01
Constraints on the curvature of nuclear symmetry energy from recent astronomical data within the KIDS framework
Hana Gil · Panagiota Papakonstantinou · Chang Ho Hyun
We investigate the density dependence of the nuclear symmetry energy $S (ρ)$ in the KIDS (Korea-IBS-Daegu-SKKU) framework for the nuclear equation of state (EoS) and energy-density functional (EDF). The aim is to constrain the value of the curvature parameter ( $K_{sym}$ ) based on recent astronomical data. First, assuming a standard saturation point, we calculate bulk nuclear properties within KIDS-EDF for different values of the compression modulus of symmetric nuclear matter ( $K_{0}$ ) and of the leading-order symmetry energy parameters, i.e., the symmetry energy ( $J$ ) and slope ( $L$ ) at saturation density, each within a broadly accepted range, as well as $K_{sym}$ . All of the above EoS parameters are varied independently of each other. The skewness parameter ( $Q_{sym}$ ) is presently kept fixed at 650 MeV. For all EoS parameter sets which describe the selected nuclear data within better than $0.3%$ , we calculate the neutron-star equation of state and mass-radius relation and analyze the results in terms of Pearson correlation coefficients $r$ . We find that the value of $K_{sym}$ is strongly correlated with the radius of both a canonical and a massive star ( $∣ r ∣ > 0.9$ ). If we impose that all known astronomical constraints on the neutron star radii must be satisfied, we deduce $- 150 < K_{sym} < 0$ . As a result, the symmetry energy as a function of the density is consistently found to have an inflection point at $ρ_{0} < ρ < 2 ρ_{0}$ . We take the opportunity to report that the neutron skin thickness of $^{208}$ Pb shows no correlation at all with the neutron star radii ( $∣ r ∣ < 0.1$ ), in contrast with studies which focus on the role of $L$ only.
nucl-thIJMPE(2022)·36 citations
02
Scission configuration in the self-consistent calculations with neck constraint
R. Han · M. Warda · A. Zdeb · L. M. Robledo
The calculations of the potential energy surface are essential in the theoretical description of the fission process. In the constrained self-consistent approach, the smooth evolution of nuclear shape is described from the ground state until a very elongated one with a narrow neck. In all microscopic calculations, the rupture of the neck at scission is associated with a substantial change of nuclear matter density distribution and rapid energy decrease. In this paper, we show that there is no discontinuity of the potential energy surface at scission when multi-constrained calculations are applied with the neck constraint. An early rupture of the neck at lower quadrupole and octupole moments is discussed as competitive with the conventional fission path. We discuss the neck properties in the scission configuration. We find that the neck radius in the asymmetric fission mode cannot decrease below 2 fm, and the nuclear matter density cannot decrease below the saturation density. In the compact fission mode, nuclear density may go down to half of the saturation density before the rupture of the neck.
nucl-thPRC(2021)·19 citations
03
Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay
He-Lei Liu · Zi-Gao Dai · Guo-Liang Lv · Akira Dohi · Gao-Chan Yong · Masa-aki Hashimoto
We study the quiescent luminosities of accreting neutron stars by a new mechanism as neutrino heating for additional deep crustal heating, where the neutrino heating is produced by charged pions decay from the nuclear collisions on the surface of neutron star during its active accretion. For low mass neutron star( $≲ 1.4 M_{⊙}$ ), as the neutrino heating is little( $≲ 1$ MeV per accreted nucleon) or there would be no neutrino heating, the quiescent luminsoity will be not affected or slightly affected. While for massive neutron star ( $≳ 2 M_{⊙}$ ), the quiescent luminosity will be enhanced more obviously with neutrino heating in the range 2-6 MeV per accreted nucleon. The observations on cold neutron stars such as 1H 19605+00, SAX J1808.4-3658 can be explained with neutrino heating if a fast cooling and heavy elements surface are considered. The observations on a hot neutron star such as RX J0812.4-3114 can be explained with neutrino heating if the direct Urca process is forbidden for a massive star with light elements surface, which is different from the previous work that the hot observations should be explained with small mass neutron star and the effect of superfluidity.
↳ astro-ph.HEnucl-thPRD(2021)·3 citations

Constraints on the curvature of nuclear symmetry energy from recent astronomical data within the KIDS framework

Scission configuration in the self-consistent calculations with neck constraint

Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay