Effects of Dissipation on Superfluid Neutron Star Oscillations

这个项目研究中子星，最终目的是将电磁波和引力波的观测结果与中子星内部的性质联系起来。中子星物质将用多流体模型来描述，其中一种流体是中子超流，据信存在于冷中子星的核心和内壳中，另一种流体是所有其他电磁带电成分(壳核、超导质子和电子)的集合体，第三种流体是熵，最后一种流体由无质量的中微子组成。我们将为牛顿超流中子星建立一组适当形式的耗散方程，并用它们的线性化形式来确定正则能量的时间变化率。在模态谱的分析中，将采用模式频率的局部色散关系和零频模式空间的分解。现实的状态方程将被使用，其中包括夹带效应(即，在中子中诱导的动量，例如，导致一些质子的质量被携带)和对称能量(这往往会迫使原子核拥有与质子一样多的中子)。将获得引力波探测器信噪比的估计，以及对潜在可观察到的模式频率如何取决于状态方程和动力学水平上的超流性/超导电性的基本理解。该项目有可能回答以下具体问题：1.对于仅由单一流体组成的系统，没有对应的多流体动力学不稳定性的一般特征是什么？这种不稳定性的天体物理后果是什么？2.超流和超导电性及其独特的耗散形式如何影响中子星的引力波发射？它们会在引力波本身留下独特且可探测到的信号吗？随着引力波天文学的出现，有必要扩大对中子星等天体物理对象建模的极限，以便最大限度地发挥对引力波数据的分析结果。通过这种方式，中子星可以最大限度地被用作天体物理实验室，研究大规模超流、真正的高温超导和超核状态方程。本科生将参与这项研究。

This project studies neutron stars for the eventual purpose of relating both electromagnetic and gravitational wave observations to the properties of the neutron star interior. The neutron star matter will be described in terms of a multi-fluid model, where one fluid is the neutron superfluid, which is believed to exist in the core and inner crust of cold neutron stars, another is a conglomerate of all other electromagnetically charged constituents (crust nuclei, superconducting protons, and electrons), the third is the entropy, and the last consists of massless neutrinos. A properly formulated set of dissipative equations for Newtonian superfluid neutron stars will be developed and their linearized form will be used to determine the time rate of change of the canonical energy. Local dispersion relations for the mode frequencies and a decomposition of the space of zero-frequency modes will be employed in the analysis of the mode spectrum. Realistic equations of state will be used that incorporate the entrainment effect (i.e. a momentum induced in the neutrons, say, causes some of the mass of the protons to be carried along) and symmetry energy (which tends to force nuclei to have as many neutrons as protons). Estimates for gravitational wave detector signal-to-noise will be obtained, as well as a basic understanding of how the potentially observable mode frequencies depend on superfluidity/superconductivity at the equation of state and dynamical levels.The project has the potential to answer the following specific questions:1. What are the generic features of multi-fluid, dynamical instabilities that have no counterpartsfor systems consisting of only a single fluid? What are the astrophysical consequencesof such instabilities?2. How do superfluidity and superconductivity, and their unique forms of dissipation, affectgravitational wave emission from neutron stars? Do they leave distinctive and detectablesignatures in the gravitational waves themselves?With the advent of gravitational wave astronomy, there is an accompanying need to push the limits of modelling of astrophysical objects like neutron stars, so as to maximize the insights that result from analyses of gravitational wave data. In this way neutron stars can be maximally utilized as astrophysical laboratories for the study of large-scale superfluidity, truely high-temperature superconductivity, and the supra-nuclear equation of state. Undergraduates will participate in this research.