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arXiv 2209.13616astro-ph.COgr-qc
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模拟暴胀宇宙:从单场到轴子-U(1)模型

Simulating the inflationary Universe: from single-field to the axion-U(1) model

Angelo Caravano

摘要:

我们提出了一个非线性研究的基础上的暴胀时代的数值格子模拟。格子模拟是原初宇宙学中的一个著名工具,它被广泛地用于研究暴胀后的再加热期。我们把这种已知的机制推广到暴胀时期。由于这是在暴胀结束之前对暴胀时期的第一次模拟,论文的第一部分集中在暴胀的最小单场模型上。我们讨论了在晶格上模拟暴胀所需的概念和技术成分。模拟是用来重现近标度不变的标量扰动谱,以及在功率谱的振荡所造成的一个步骤的潜力。在第二部分中,我们重点讨论了更复杂的轴子-U(1)模型,并给出了该模型在深暴胀时期的第一个格子模拟。我们使用模拟发现新的性质的原始标量扰动从这个模型。在线性政权的理论,我们发现高阶非高斯性(超越三谱)的关键是描述标量扰动的统计特性。相反,我们发现扰动是近高斯的非线性制度的理论。这放松了现有的限制,从原始黑洞的过度生产,允许引力波信号在可观察范围内即将到来的实验,如LISA。我们的结果表明,格子模拟可以成为一个强大的工具,研究暴胀时代及其观测签名。

英文摘要:

We present a nonlinear study of the inflationary epoch based on numerical lattice simulations. Lattice simulations are a well-known tool in primordial cosmology, and they have been extensively used to study the reheating epoch after inflation. We generalize this known machinery to the inflationary epoch. Being this the first simulation of the inflationary epoch much before the end of inflation, the first part of the thesis focuses on the minimal single-field model of inflation. We discuss the conceptual and technical ingredients needed to simulate inflation on a lattice. The simulation is used to reproduce the nearly scale-invariant spectrum of scalar perturbations, as well as the oscillations in the power spectrum caused by a step in the potential. In the second part, we focus on the more complicated axion-U(1) model of inflation and present the first lattice simulation of this model during the deep inflationary epoch. We use the simulation to discover new properties of primordial scalar perturbations from this model. In the linear regime of the theory, we find high-order non-Gaussianity (beyond trispectrum) to be key to describing the statistical properties of scalar perturbations. Conversely, we find perturbations to be nearly Gaussian in the nonlinear regime of the theory. This relaxes existing constraints from the overproduction of primordial black holes, allowing for a gravitational waves signal in the observable range of upcoming experiments such as LISA. Our results show that lattice simulations can be a powerful tool to study the inflationary epoch and its observational signatures.

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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