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arXiv 1707.00147nucl-thastro-ph.HE
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考虑致密恒星物质中热核蒸发的平衡核系综

Equilibrium nuclear ensembles taking into account vaporization of hot nuclei in dense stellar matter

Shun Furusawa, Igor Mishustin

备注：
27pages, 8 figures, accepted for publication in Phys. Rev. C
发表信息：
Phys. Rev. C 97, 025804 (2018)
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摘要：

本文研究了稠密高温恒星环境中由核子和全核混合组成的核物质的高温效应。单个核内描述的可压缩液滴模型是基于Skyrme相互作用的体积能量，并考虑到在有限的温度和密度的表面和库仑能量的修改。自由能量密度相对于所有重核的单个平衡密度和核成分最小。我们发现，它们的优化平衡密度变得越来越小，在高温下，因为增加的热贡献的体积自由能和表面能的减少。富中子核在某些温度下变得不稳定并相继消失。对两组模型参数进行了计算，导致核对称能中斜率参数的不同值。结果表明，较大的斜率参数降低了平衡密度和熔化温度。我们还将新模型与其他一些方法进行了比较，发现以前忽略蒸发的计算在$T \lesssim 10$ MeV处低估了重核的质量分数，而在$T\gtrsim10$ ~MeV处高估了重核的质量分数.为了建立爆炸性天体物理现象的状态方程，需要进一步完善核蒸发和轻团簇的计算。

英文摘要：

We investigate the high-temperature effect on the nuclear matter that consists of mixture of nucleons and all nuclei in the dense and hot stellar environment. The individual nuclei are described within the compressible liquid-drop model that is based on Skyrme interactions for bulk energies and that takes into account modifications of the surface and Coulomb energies at finite temperatures and densities. The free-energy density is minimized with respect to the individual equilibrium densities of all heavy nuclei and the nuclear composition. We find that their optimized equilibrium densities become smaller and smaller at high temperatures because of the increase of thermal contributions to bulk free energies and the reduction of surface energies. The neutron-rich nuclei become unstable and disappear one after another at some temperatures. The calculations are performed for two sets of model parameters leading to different values of the slope parameter in the nuclear symmetry energy. It is found that the larger slope parameter reduces the equilibrium densities and the melting temperatures. We also compare the new model with some other approaches and find that the mass fractions of heavy nuclei in the previous calculations that omit vaporization are underestimated at $T \lesssim 10$MeV and overestimated at $T\gtrsim10$~MeV. The further sophistication of calculations of nuclear vaporization and of light clusters would be required to construct the equation of state for explosive astrophysical phenomena.

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