Nuclear Theory·nucl-th

Thursday·February 9, 2023

7 papers—3 primary·4 cross-listed

01
Direct triple- $α$ process in non-adiabatic approach
M. Katsuma
Triple- $α$ reaction rates have been determined well with the sequential process via the narrow resonances. However, the direct triple- $α$ process at off-resonant energies still remains in unsolved problems. In the present report, the direct triple- $α$ contribution is estimated with a non-adiabatic method, and it is found to be 10 $^{- 15}$ --10 $^{- 3}$ pb order in photodisintegration cross sections of $^{12}$ C(2 $_{1}^{+} \to$ 0 $^{+}$ ) for $0.15 < E < 0.35$ MeV. This is far below the values predicted by the recent adiabatic models. In spite of the large difference, the derived rates are found to be concordant with NACRE at the helium burning temperatures.
nucl-thastro-ph.SRnucl-ex1 citation
02
Three-dimensional potential energy surface for fission of $^{236}$ U within covariant density functional theory
Ming-Hui Zhou · Ze-Yu Li · Sheng-Yuan Chen · Yong-Jing Chen · Zhi-Pan Li
We have calculated the three-dimensional potential energy surface (PES) for the fission of compound nucleus $^{236}$ U using the covariant density functional theory with constraints on the axial quadrupole and octupole deformations $(β_{2}, β_{3})$ as well as the nucleon number in the neck $q_{N}$ . By considering the additonal degree of freedom $q_{N}$ , coexistence of the elongated and compact fission modes is predicted for $0.9 ≲ β_{3} ≲ 1.3$ . Remarkably, the PES becomes very shallow across a large range of quadrupole and octupole deformations for small $q_{N}$ , and consequently, the scission line in $(β_{2}, β_{3})$ plane will extend to a shallow band, which leads to a fluctuation for the estimated total kinetic energies by several to ten MeV and for the fragment masses by several to about ten nucleons.
nucl-thCPC(2023)·3 citations
03
Systematic analysis of the impacts of symmetry energy parameters on neutron star properties
N. K. Patra · Anagh Venneti · Sk Md Adil Imam · Arunava Mukherjee · B. K. Agrawal
The impacts of various symmetry energy parameters on the properties of neutron stars (NSs) have been recently investigated, and the outcomes are at variance, as summarized in Table III of Phys. Rev. D 106, 063005 (2022). We have systematically analyzed the correlations of slope and curvature parameters of symmetry energy at the saturation density ( $ρ_{0} = 0.16 fm^{- 3}$ ) with the tidal deformability and stellar radius of non-spinning neutron stars in the mass range of $1.2 - 1.6 M_{⊙}$ using a large set of minimally constrained equations of state (EoSs). The EoSs at low densities correspond to the nucleonic matter and are constrained by empirical ranges of a few low-order nuclear matter parameters from the finite nuclei data and the pure neutron matter EoS from chiral effective field theory. The EoSs at high densities ( $ρ > 1.5 - 2 ρ_{0}$ ) are obtained by a parametric form for the speed of sound that satisfies the causality condition. Several factors affecting the correlations between the NS properties and the individual symmetry energy parameters usually encountered in the literature are considered. These correlations are quite sensitive to the choice of the distributions of symmetry energy parameters and their interdependence. But, variations of NS properties with the pressure of $β -$ equilibrated matter at twice the saturation density remain quite robust which maybe due to the fact that the pressure depends on the combination of multiple nuclear matter parameters that describe the symmetric nuclear matter as well as the density dependence of the symmetry energy. Our results are practically insensitive to the behavior of EoS at high densities.
nucl-thastro-ph.HEastro-ph.SRgr-qc+1PRC(2023)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE

Direct triple-α process in non-adiabatic approach

Three-dimensional potential energy surface for fission of 236U within covariant density functional theory

Systematic analysis of the impacts of symmetry energy parameters on neutron star properties

Affiliations

Direct triple- $α$ process in non-adiabatic approach

Three-dimensional potential energy surface for fission of $^{236}$ U within covariant density functional theory