AI 中文总结
该研究证实镜像暗物质双流体中子星的外层流体主导基频与致密性的普适关系成立，还发现内层流体主导基频的普适关系，Cowling近似对其频率估计表现更优，或可用于约束暗物质质量分数。
AI 中文摘要
普适关系是在存在各种不确定性时，从中子星观测中提取物理信息的特别有用的方法，它能减少对不确定模型参数和微物理输入的依赖。本研究采用双流体描述方法，研究了掺有镜像暗物质的中子星的振荡频率，其中外层流体和内层流体产生两个不同的基频。我们证实，先前针对自相互作用暗物质掺混中子星建立的外层流体主导模式的质量标度基频与恒星致密性之间的普适关系，在镜像暗物质场景中同样成立。然而，与Cowling近似下的相应结果相比，当包含度规微扰时，该普适关系的稳健性会降低。我们进一步发现，只要暗物质质量分数固定，内层流体主导的基频也可表示为与致密性相关的关系，且在很大程度上与普通物质的物态方程无关。这些结果表明，同时探测两个基频可以提供一种在普通物质物态方程仍不确定的情况下约束暗物质质量分数的方法。最后，我们发现，Cowling近似对外层流体相关基频的估计精度与不含暗物质的标准中子星相当，而对内层流体相关频率的估计表现甚至更好。
英文摘要
Universal relations provide a particularly useful way to extract physical information from neutron star observables in the presence of various uncertainties by reducing the dependence on uncertain model parameters and microphysical inputs. In this study, we examine the oscillation frequencies of mirror dark matter admixed neutron stars using a two-fluid description, where the outer and inner fluids give rise to two distinct fundamental frequencies. We confirm that the universal relation between the mass-scaled fundamental frequency of the outer-fluid-led mode and the stellar compactness, established previously for self-interacting dark matter admixed neutron stars, also holds in the mirror dark matter scenario. However, this universal relation becomes less robust when metric perturbations are included, compared with the corresponding results in the Cowling approximation. We further find that the inner-fluid-led fundamental frequency can also be expressed as a compactness-dependent relation that is largely independent of the normal matter equation of state, provided that the dark matter mass fraction is fixed. These results suggest that the simultaneous detection of the two fundamental frequencies could provide a way to constrain the dark matter mass fraction, even when the equation of state of normal matter remains uncertain. Finally, we find that the Cowling approximation estimates the fundamental frequency associated with the outer fluid with an accuracy comparable to that found for standard neutron stars without dark matter, while it performs even better for the frequency associated with the inner fluid.
