Effects of Dissipation on Superfluid Neutron Star Oscillations

该项目研究中子星的最终目的是将电磁和引力波观测与中子星内部的特性联系起来。中子星物质将以多流体模型来描述，其中一种流体是中子超流体，它被认为存在于冷中子星的核心和内部地壳中，另一种是所有其他电磁带电成分（地壳核，超导质子和电子）的混合物，第三种是熵，最后一种由无质量的中微子组成。本文将建立牛顿超流体中子星的一组耗散方程，并利用它们的线性化形式来确定正则能的时间变化率。模态频谱分析将采用模态频率的局部色散关系和零频率模态空间的分解。现实的状态方程将被使用，包括夹带效应（例如，在中子中产生的动量，比如，导致一些质子的质量被携带）和对称能（它倾向于迫使原子核拥有和质子一样多的中子）。将获得引力波探测器信噪比的估计，以及对潜在可观测模式频率如何依赖于状态方程和动力学水平上的超流动性/超导性的基本理解。该项目有可能回答以下具体问题：1。多流体动力学不稳定性的一般特征是什么，而只有一种流体组成的系统没有相应的不稳定性？这种不稳定性的天体物理学后果是什么？超流动性和超导性及其独特的耗散形式如何影响中子星的引力波发射？它们是否在引力波本身留下了独特的、可探测的特征？随着引力波天文学的出现，随之而来的需要是突破中子星等天体物理物体建模的极限，以便最大限度地从引力波数据分析中获得见解。这样就可以最大限度地利用中子星作为研究大尺度超流体、真正的高温超导性和超核状态方程的天体物理实验室。本科生将参与本研究。

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.