一个完整超新星状态方程的统计模型
Statistical Model for a Complete Supernova Equation of State
摘要：
提出了一个状态方程和超新星物质组成的统计模型，重点讨论了核物质的液-气相变。它由处于核统计平衡的原子核和相互作用核子的系综组成。核子采用相对论平均场模型。原子核的质量取自基于相同原子核拉格朗日量的原子核结构计算。对于已知的核，直接使用实验数据。排除体积效应的实施在一个热力学一致的方式，使过渡到均匀的核物质在大密度可以描述。因此，该模型可以适用于所有与超新星模拟相关的密度，即ρ =10^5 - 10^15 g/cm ^3，并且有可能计算出完整的超新星EOS表。该模型允许调查壳效应的作用，这导致周围的中子幻数为低温窄峰分布。在较高的温度下，分布变得广泛。的统计处理和核分布的组合物的意义示出。我们发现，光团簇的贡献是非常重要的，只有很少的α粒子单独代表。的EOS的结果进行了系统的比较，两个常用的超新星物质模型是基于单核近似。除了组成外，一般来说，不同的EOS之间只有很小的差异，这种差异在（低密度）液-气相变线附近最明显，在那里，光和中间团簇的分布有重要的影响。讨论了该模型可能的扩展和改进。
英文摘要：
A statistical model for the equation of state (EOS) and the composition of supernova matter is presented with focus on the liquid-gas phase transition of nuclear matter. It consists of an ensemble of nuclei and interacting nucleons in nuclear statistical equilibrium. A relativistic mean field model is applied for the nucleons. The masses of the nuclei are taken from nuclear structure calculations which are based on the same nuclear Lagrangian. For known nuclei experimental data is used directly. Excluded volume effects are implemented in a thermodynamic consistent way so that the transition to uniform nuclear matter at large densities can be described. Thus the model can be applied at all densities relevant for supernova simulations, i.e. rho=10^5 - 10^15 g/cm^3, and it is possible to calculate a complete supernova EOS table. The model allows to investigate the role of shell effects, which lead to narrow-peaked distributions around the neutron magic numbers for low temperatures. At larger temperatures the distributions become broad. The significance of the statistical treatment and the nuclear distributions for the composition is shown. We find that the contribution of light clusters is very important and is only poorly represented by alpha-particles alone. The results for the EOS are systematically compared to two commonly used models for supernova matter which are based on the single nucleus approximation. Apart from the composition, in general only small differences of the different EOSs are found. The differences are most pronounced around the (low-density) liquid-gas phase transition line where the distribution of light and intermediate clusters has an important effect. Possible extensions and improvements of the model are discussed.
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