发表机构
SISSA - International School for Advanced Studies; INFN – National Institute for Nuclear Physics; IFPU, Institute for Fundamental Physics of the Universe; INAF, Osservatorio Astronomico di Trieste; ICSC - Italian Research Center on High Performance Computing, Big Data and Quantum Computing（国际高等研究院; 意大利国家核物理研究所; 宇宙基础物理研究所; 的里雅斯特天文台; 意大利高性能计算、大数据和量子计算研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过弱引力透镜会聚功率谱约束原初磁场，构建仿真器并利用MCMC分析，对磁场振幅和谱指数给出上限并揭示参数简并。
AI 中文摘要
将原初磁场（PMFs）引入标准宇宙学模型ΛCDM，会在线性层面影响物质功率谱，导致小尺度上的功率增强。在本工作中，我们将增强后的谱作为仅含暗物质的N体模拟的初始条件，并研究其非线性演化。根据得到的非线性物质功率谱，我们计算了弱引力透镜的会聚功率谱（Cκ），并展示了PMFs的存在如何导致高多极矩处的增强。随后，我们构建了一个包含内禀取向和重子反馈的Cκ仿真器（emulator）。我们使用针对不同PMF模型以及三个最大多极矩值（ℓmax=5000、10000和20000）生成的模拟数据进行了MCMC分析。PMF模型由定义磁场幂律功率谱PB(k)∝B1Mpc^2 k^{nB}的两个参数表征，其中B1Mpc是1 Mpc尺度上的振幅，nB是功率谱指数。对于对应B1Mpc=0的ΛCDM模拟数据，我们在95%置信水平下分别获得了B1Mpc<1.6、1.0和0.8 nG的近似上限（对应三个ℓmax值）。对于非零输入磁场，B1Mpc和nB的恢复强烈依赖于PMF模型和所考虑的最大多极矩。nB=-2.1的模型比nB=-2.7的模型更容易被约束，因为它们对会聚功率谱产生更强的增强效应。我们发现PMF参数与内禀取向或重子反馈参数之间没有明显的简并，而B1Mpc和nB之间可能存在简并。我们通过对选定的二维后验分布进行线性拟合来刻画这种简并。
英文摘要
Introducing primordial magnetic fields (PMFs) into the standard cosmological model, $Λ$CDM, has an impact on the matter power spectrum at the linear level, resulting in an increase of power on small scales. In this work, we use the enhanced spectrum as the initial condition for dark-matter-only N-body simulations and study its non-linear evolution. From the resulting non-linear matter power spectrum, we calculate the convergence power spectrum of weak lensing ($C_κ$) and show how the presence of PMFs causes an enhancement at high multipoles. We then construct an emulator for $C_κ$ that also includes intrinsic alignment and baryon feedback. We perform MCMC analyses using mock data generated for different PMF models and for three values of the maximum multipole, $\ell_{\rm max}=5000$, $10000$, and $20000$. The PMFs models are characterized by the two parameters that define the power-law power spectrum of the magnetic field $P_B(k)\propto B_{\rm 1Mpc}^2 k^{n_B}$, where $B_{\rm 1Mpc}$ is the amplitude at a scale of $1$ Mpc and $n_B$ is the power spectral index. For $Λ$CDM mocks, corresponding to $B_{\rm 1Mpc}=0$, we obtain approximate upper limits of $B_{\rm 1Mpc}<1.6$, $1.0$, and $0.8\,{\rm nG}$ at the $95\%$ confidence level for the three values of $\ell_{\rm max}$ respectively. For non-zero input magnetic fields, the recovery of $B_{\rm 1Mpc}$ and $n_B$ depends strongly on the PMFs model and on the maximum multipole considered. Models with $n_B=-2.1$ are more easily constrained than models with $n_B=-2.7$, since they produce a stronger enhancement of the convergence power spectrum. We find no clear degeneracy between the PMFs parameters and the intrinsic alignment or baryon feedback parameters, while $B_{\rm 1Mpc}$ and $n_B$ can be degenerate. We characterize this degeneracy through linear fits to selected $2$D posterior distributions.
