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arXiv 1703.01433nucl-thastro-ph.SRnucl-exphysics.comp-ph
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量子核面食与核对称能

Quantum Nuclear Pasta and Nuclear Symmetry Energy

F. J. Fattoyev, C. J. Horowitz, B. Schuetrumpf

摘要:

复杂而奇特的核几何形状预计将自然出现在密集的核物质中,这些物质发现于中子星和超新星环境的地壳中,统称为核面食。pasta几何依赖于平均重子密度、质子分数和温度,并且在确定超新星和中子星地壳中物质的许多输运性质方面至关重要。使用一组自洽的微观核能密度泛函,我们提出的第一个结果的大规模量子模拟的面食阶段在重子密度$0.03 \leq ρ\leq 0.10$ FM $^{-3}$,质子分数$0.05 \leq Y_p \leq 0.40$,和零温度。特别是完整的量子模拟,使我们能够彻底调查的作用和影响的核对称性能量的面食配置。我们使用Sky 3D代码,解决了三维笛卡尔网格上的Skyrme Hartree-Fock方程。对于核相互作用,我们使用最先进的UNEDF 1参数化,这是介绍了研究大变形的核,因此是适合的核面食的研究。核对称能的密度依赖性是通过调整两个纯粹的isovector观测值,是不敏感的,目前可用的实验数据模拟。我们发现,一个最小的核子总数$A=2000$是必要的,以防止包含虚假壳效应的结果,并尽量减少有限尺寸的影响。我们发现,在中子星壳中存在着多种核面几何结构,其结果强烈依赖于核对称能。随着质子分数的增加,核对称能的影响不那么明显。在$T=0$ MeV的量子核面食计算被证明很容易陷入亚稳态,并讨论了可能的补救措施,以避免亚稳态的解决方案。

英文摘要:

Complex and exotic nuclear geometries are expected to appear naturally in dense nuclear matter found in the crust of neutron stars and supernovae environment collectively referred to as nuclear pasta. The pasta geometries depend on the average baryon density, proton fraction and temperature and are critically important in the determination of many transport properties of matter in supernovae and the crust of neutron stars. Using a set of self-consistent microscopic nuclear energy density functionals we present the first results of large scale quantum simulations of pasta phases at baryon densities $0.03 \leq ρ\leq 0.10$ fm$^{-3}$, proton fractions $0.05 \leq Y_p \leq 0.40$, and zero temperature. The full quantum simulations, in particular, allow us to thoroughly investigate the role and impact of the nuclear symmetry energy on pasta configurations. We use the Sky3D code that solves the Skyrme Hartree-Fock equations on a three-dimensional Cartesian grid. For the nuclear interaction we use the state of the art UNEDF1 parametrization, which was introduced to study largely deformed nuclei, hence is suitable for studies of the nuclear pasta. Density dependence of the nuclear symmetry energy is simulated by tuning two purely isovector observables that are insensitive to the current available experimental data. We find that a minimum total number of nucleons $A=2000$ is necessary to prevent the results from containing spurious shell effects and to minimize finite size effects. We find that a variety of nuclear pasta geometries are present in the neutron star crust and the result strongly depends on the nuclear symmetry energy. The impact of the nuclear symmetry energy is less pronounced as the proton fractions increase. Quantum nuclear pasta calculations at $T=0$ MeV are shown to get easily trapped in meta-stable states, and possible remedies to avoid meta-stable solutions are discussed.

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