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arXiv 2307.04798astro-ph.COastro-ph.IM
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宇宙弦在宇宙微波背景中诱导各向异性的快速仿真

Fast emulation of anisotropies induced in the cosmic microwave background by cosmic strings

Matthew A. Price, Matthijs Mars, Matthew M. Docherty, Alessio Spurio Mancini, Augustin Marignier, Jason. D. McEwen

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AI总结：

本文提出利用小波相位谐波作为潜在表示，在单GPU上快速仿真宇宙弦诱导的CMB各向异性，生成高保真且统计正确的样本，适用于基于模拟的推断。

摘要：

宇宙弦是线性拓扑缺陷，可能是在极早期宇宙的对称性破缺相变过程中产生的。在膨胀的宇宙中，因果分离区域的存在阻止了这些对称性被均匀地破缺，因此不可避免地会形成一个宇宙弦网络。为了忠实地生成此类过程的观测结果，需要进行计算成本高昂的数值模拟，这阻碍了许多类型的分析。我们提出了一种技术，可以快速仿真观测结果，从而绕开模拟。仿真是一种生成式建模形式，通常建立在机器学习骨干之上。端到端的仿真常常因高维性和训练数据不足而失败。因此，常见的做法是仿真一个潜在表示，从中可以轻松合成观测结果。小波相位谐波是宇宙学场的优秀潜在表示，既可作为汇总统计量，也可用于仿真，因为它们不需要训练，并且对非高斯信息高度敏感。利用小波相位谐波作为潜在表示，我们开发了在单个GPU上不到一分钟内，在7.2度视场、亚角秒分辨率下仿真弦诱导的CMB各向异性的技术。除了生成高保真仿真外，我们还提供了一种技术来确保这些观测结果正确分布，从而提供更具代表性的样本集合。我们的仿真统计与在全面的Nambu-Goto模拟上计算的统计结果相当。我们的发现表明，这些快速仿真方法可能适用于广泛用途，例如基于模拟的推断流程。我们将代码提供给社区，以便研究人员能够快速仿真宇宙弦诱导的CMB各向异性，用于他们自己的分析。

英文摘要：

Cosmic strings are linear topological defects that may have been produced during symmetry-breaking phase transitions in the very early Universe. In an expanding Universe the existence of causally separate regions prevents such symmetries from being broken uniformly, with a network of cosmic string inevitably forming as a result. To faithfully generate observables of such processes requires computationally expensive numerical simulations, which prohibits many types of analyses. We propose a technique to instead rapidly emulate observables, thus circumventing simulation. Emulation is a form of generative modelling, often built upon a machine learning backbone. End-to-end emulation often fails due to high dimensionality and insufficient training data. Consequently, it is common to instead emulate a latent representation from which observables may readily be synthesised. Wavelet phase harmonics are an excellent latent representations for cosmological fields, both as a summary statistic and for emulation, since they do not require training and are highly sensitive to non-Gaussian information. Leveraging wavelet phase harmonics as a latent representation, we develop techniques to emulate string induced CMB anisotropies over a 7.2 degree field of view, with sub-arcminute resolution, in under a minute on a single GPU. Beyond generating high fidelity emulations, we provide a technique to ensure these observables are distributed correctly, providing a more representative ensemble of samples. The statistics of our emulations are commensurate with those calculated on comprehensive Nambu-Goto simulations. Our findings indicate these fast emulation approaches may be suitable for wide use in, e.g., simulation based inference pipelines. We make our code available to the community so that researchers may rapidly emulate cosmic string induced CMB anisotropies for their own analysis.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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