致密恒星物质组分相对丰度对核对称能的依赖性
Dependence of relative abundances of constituents in dense stellar matter on nuclear symmetry energy
摘要：
对于一个致密的恒星物质，它是电中性的，处于β平衡，电子化学势，μ_e，将非常依赖于重子物质密度。一般认为，随着密度的增加，电子化学势将增加，随着μ e变得与它们的能量标度相当，将出现新的自由度。假设恒星物质的电中性和β平衡，我们研究了在不同的核相互作用模型下，轻子化学势的密度依赖性如何变化，这些模型被实验限制到核物质密度n_0，但推断不同并计算了核子的相对丰度（中子和质子）和轻子（电子和μ子）以及它们的密度依赖性。我们发现电子化学势的密度依赖性强烈地依赖于与核物质状态方程的软/硬相关的核对称性能量的结构，该状态方程测量与中子-质子不对称性相关的能量。因此，中子、质子、电子和μ子的相对丰度以及K介子凝聚强烈依赖于核对称能。在我们的发现中，一个有趣的结果是，与公认的知识相反，中子星物质中的K介子凝聚，这被认为是超过n_0的第一个相变，并在致密星形成的某些情况下起着至关重要的作用，是不是直接联系到超过n_0的状态方程的软或硬。这一点可以用一个“超软”状态方程来说明，该状态方程与GSI的pi^-/pi^+比值数据相拟合，其中排除了任何密度下的K介子凝聚。
英文摘要：
For a dense stellar matter, which is electrically neutral and in beta equilibrium, the electron chemical potential, mu_e, will depend nontrivially on baryonic matter density. It is generally expected that as density increases, the electron chemical potential will increase and new degrees of freedom will emerge as mu_e becomes comparable to their energy scales. Assuming the electrical neutrality and beta equilibrium for the stellar matter, we have studied how the density dependence of lepton chemical potentials varies for different models of nuclear interactions that are constrained by experiments up to nuclear matter density, n_0, but extrapolate differently(unconstrained) beyond n_0 and calculated the relative abundances of nucleons(neutron and proton) and leptons(electron and muon) and their density dependencies. We find that the density dependence of the electron chemical potential is strongly dependent on the structure of the nuclear symmetry energy relevant to softness/stfness of the nuclear matter EOS that measures the energy relevant to the neutron-proton asymmetry. As a consequence, the relative abundances of neutrons, protons, electrons, and muons as well as the kaon condensation are strongly dependent on the nuclear symmetry energy. An intriguing result in our finding is that contrary to the accepted lore, kaon condensation in neutron star matter, which is considered to be the first phase transitions beyond n_0 and plays a crucial role in certain scenarios of compact-star formation, is not directly tied to the softness or stiffness of the EOS beyond n_0. This point is illustrated with a "super-soft" EOS that is fit to the pi^-/pi^+ ratio data of GSI which excludes kaon condensation at any density.
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