中微子是宇宙中最基本的粒子，宇宙大爆炸后不久产生的残余中微子是宇宙中最丰富的粒子之一。由此中微子会对宇宙现象有所影响，包括宇宙微波背景（CMB）和大尺度结构（LSS）。中微子还有可能是联系标准宇宙模型和暗物质的通道，在现代宇宙学中，对中微子的研究仍然是一个很重要的部分。
随着科技的进步和超级计算机的发展，为科学探索带来了强大的工具，也给研究人员对宇宙学大尺度结构（LSS）的高精度研究提供了可能性。计算机模拟在宇宙学领域开始发挥着越来越重要的作用，成为理论和观测的桥梁。
本文研究使用的数据来自宇宙学数值模拟程序 TianNu 和 TianZero。程序 TianNu 是在TianZero 基础上的优化改进，并提升大尺度结构上的精度和规模，运行于超级计算机天河二号。 TianNu 支持 CDM 粒子和中微子的共同演化，比以往的中微子模拟规模提高了两个数量级，包含 6912³ 个 CDM 粒子和 13824³ 个中微子粒子，共 2.97 万亿粒子。
本文主要研究中微子对暗物质晕及其角动量的影响，需要通过数值方法解析暗物质晕，并详细研究中微子对其的影响。首先需要关注的是暗晕的基本统计性质，主要包含相关参数和选取匹配暗晕对。对 TianNu 模拟结果进行数据处理，并与 TianZero（不含中微子）数据进行匹配，从中选取 2.5×10⁷ 个暗晕，进行分析对比。我们发现在有中微子的情况下，超过一半的暗晕（54.86%）质量低于无中微子的情况，特别是在大质量端（质量Mz ≥ 5 × 10¹⁴M⊙）。
然后再探讨中微子对暗晕角动量（AM）的影响。角动量是描述暗晕绕轴旋转时的动量表现，具有大小和方向。而角动量大小和暗晕质量、旋转速度以及旋转轴之间的距离有关。我们发现，总体而言暗晕的质量越小，中微子对暗晕角动量大小的影响越明显。而对于角动量的方向改变，中微子对角度的影响并不明显。不过总趋势上，则和中微子对角动量大小的影响相反，随着暗晕质量的增大，中微子对角动量角度影响随之增大。
我们进一步细化研究，同一暗晕的角动量 AM 模量和中微子引起的角度变化。具体来说，在中微子的影响下，同一暗晕的 PMR 模量（粒子质量降低 AM 模量）、 HMR 模量（晕质量降低 AM 模量）、其质量和方位都会因为中微子加入而发生变化。 89.71% 的含中微子的暗晕具有更小的 PMR 模量 ∆Je/Jez， 60.31% 的晕具有更小的 HMR 模量 ∆ej/ejz。在平均水平上，超过 85% ∆J/Jz 和 ∆J/Jz/Mez 是负方向，平均值分别为 -0.37% 和 4.6 × 10^-6。而大约 90% 的方向偏移小于 0.4◦， 95.44% 的晕角动量其改变角度小于 0.65◦。
最后通过比较空洞中的暗晕和宇宙中密度较高区域的暗晕来寻找对环境的依赖性。将不同尺度（50h^-1Mpc 块区）和 ( 10h^-1Mpc 区域）晕团划分成多个立方体，研究暗晕的质量平均 AM 模量 (∆JMR) 的差异。密集区域中晕团 ∆JMR 的降低的比稀疏区域中的降低更明显（高出两倍）。而稀疏环境中的暗晕普遍比密集环境的晕具有更大的角动量。这意味着在密度较高的晕团环境附近中微子的浓度更高。 ∆JMR 在大多数区块中都是负的，这与添加的中微子会降低平均 JMR 相呼应。这一区别表明，中微子对高密度环境的晕 AM模量有更大的影响，对大质量晕的影响也更明显。所以我们推论中微子对暗晕的角动量的作用会受到暗晕区域疏密分布的影响。空洞中暗晕普遍具有更大的角动量，然而中微子会导致空洞中晕的角动量减少，同时增加丝状物和壁中晕的角动量。
 

Neutrino is one of the most basic particles in the universe. The residual neutrinos produced shortly after the Big Bang are the most abundant particles in the universe after photons. Therefore, they may affect cosmic phenomena, including cosmic microwave background (CMB) and large scale structure (LSS). Therefore, it is still a great challenge to limit the mass of neutrino in modern physics. However, with the progress of science and technology and the development of supercomputers, it is possible for researchers to accurately detect large-scale structure (LSS) in cosmology. Neutrinos may also be the channel connecting the standard model and dark matter,and the numerical simulation of the nonlinear evolution of cold dark matter and neutrinos plays an important role in this process.
We will introduce the basic information, program structure and usage of TianNu's original code program cubep3m. Here is mainly as background information to provide, and mainly explain our code improvement and optimization. Based on the original cosmological simulation of TianZero, we improve the accuracy and scale of large-scale structural cosmology model, called TianNu. It is the largest cosmological N-body numerical simulation in the world. The supercomputer Tianhe-2 The scale of the previous neutrino simulation was increased by two orders of magnitude. 6912³CDM particles and 13824³ neutrino particles were evolved in the cubic volume,including 2.97 trillion particles.
After data preprocessing and data mining algorithm, many dark halo data are analyzed. We discuss the influence of neutrino on the angular momentum of dark matter halo. The first thing to pay attention to is the basic statistical properties of dark halos, which mainly include relevant parameters and dark halo data, and then conduct data analysis and discussion. Perform data processing on the simulation results of TianNu and select 2.5×107 dark halos, and match them with halos in TianZero (excluding neutrinos) for comparative analysis.
Then we will explore the influence of neutrinos on the halo angular momentum (AM). We found that neutrinos have a significant impact on the magnitude of small mass dark halo angular momentum, while larger masses have smaller changes in the direction of dark halo angular momentum. The larger the dark halo mass, the more influence neutrinos have on it. Over 89.71% of halos have smaller particle-mass-reduced AM moduli (PMR moduli), over 60.31% have smaller halo-mass-reduced AM moduli (HMR moduli), and over 95.44% change their orientations of less than 0.65◦.
Finally, we investigated its dependence on the environment. By dividing the density of halo clusters at different scales (50h^-1Mpc blocks and 10h^-1Mpc cells) into cubes, we found that in denser blocks, the decrease in average AM modulus (∆ JMR) per halo cluster with and without neutrinos in dense cells was more significant than in sparse cells. In sparse blocks with more average and similar halo attributes, this reduction is very insignificant. From the two-level divisions, we discover that in denser cubes, the decrease of mean HMR moduli with neutrinos of halos within the densest and sparsest cells is more significant (twice higher) than in sparse cubes. This distinction suggests that neutrinos exert heavier influence on AM moduli in compact regions. With neutrinos, over half halos (54.86%) have lower masses than without neutrinos, in particular in the massive end (73.50% for halos with mass Mz ≥ 5 × 10¹⁴M⊙). By studying its dependence on the environment, it is found that the dark halo in the sparse region generally has greater angular momentum than in the dense region.