标题： 宇宙膨胀后振荡子形成产生的引力波谱 显示英文标题

标题： Gravitational wave spectra from oscillon formation after inflation

摘要： 我们系统地研究了具有支持振子势的单场暴胀的再加热行为。 我们计算了发出的引力波（GWs）的特性以及产生的振子的数量密度和特征。 通过对多种势类型的数值模拟，我们将分析的势分为两类，每一类都包含具有不同大场或小场依赖性的势。 我们发现，发出的GW谱的形状和幅度具有普遍特征，在暴胀子振荡周期内，峰值位于物理波数$k/a \sim m$处，无论势的具体形状如何。 这可以作为推断暴胀后剧烈再加热阶段和可能振子形成的明确证据。 尽管存在这种明显的普遍性，我们发现在两类势之间发出的GW谱的形状存在差异，导致它们之间有区分特征。 特别是，所有势在振子形成时都会在GW谱中出现双峰结构。 然而，表现出高效参数共振的势倾向于模糊这一结构，并在模拟结束时，GW谱表现出一个单一的宽峰。 我们进一步计算了每种势产生的振子的特性，发现稳定振子和瞬时高密度的数目密度和尺寸分布存在差异。 我们进行了线性扰动分析，并使用Floquet图将模拟结果与参数共振的结构联系起来。 我们发现标量扰动的增长率和相关的振子形成时间对小场势的形状敏感，而振子的宏观物理性质（例如总数量）则取决于大场势的形状。 显示英文摘要

摘要： We systematically investigate the preheating behavior of single field inflation with an oscillon-supporting potential. We compute the properties of the emitted gravitational waves (GWs) and the number density and characteristics of the produced oscillons. By performing numerical simulations for a variety of potential types, we divide the analyzed potentials in two families, each of them containing potentials with varying large- or small-field dependence. We find that the shape and amplitude of the emitted GW spectrum have a universal feature, with the peak around the physical wavenumber $k/a \sim m$ at the inflaton oscillation period, irrespective of the exact potential shape. This can be used as a smoking-gun for deducing the existence of a violent preheating phase and possible oscillon formation after inflation. Despite this apparent universality, we find differences in the shape of the emitted GW spectra between the two potential families, leading to discriminating features between them. In particular, all potentials show the emergence of a two-peak structure in the GW spectrum, arising at the time of oscillon formation. However, potentials exhibiting efficient parametric resonance tend to smear out this structure and by the end of the simulation the GW spectrum exhibits a single broad peak. We further compute the properties of the produced oscillons for each potential, finding differences in the number density and size distribution of stable oscillons and transient overdensities. We perform a linear fluctuation analysis and use Floquet charts to relate the results of our simulations to the structure of parametric resonance. We find that the growth rate of scalar perturbations and the associated oscillon formation time are sensitive to the small-field potential shape while the macroscopic physical properties of oscillons (e.g. total number) depend on the large-field potential shape.