标题： 坍塌域墙的近峰值引力波谱 显示英文标题

标题： Near-Peak Spectrum of Gravitational Waves from Collapsing Domain Walls

摘要： 宇宙学畴壁出现在许多标准模型的自然扩展中。 如果产生，它们会迅速进入自相似标度状态，在此状态下，它们能够有效地产生随机引力波背景。 为了避免宇宙灾难，它们必须在能量密度产生不利影响之前衰变。 在这里，我们提供了一组格子模拟，全面研究了这一衰变阶段畴壁网络的引力波特征。 畴壁最初通过自发打破$\mathbb{Z}_2$对称性形成，随后通过一个小的偏置项的作用衰变，该偏置项导致假真空区域坍缩。 我们发现，在整个坍缩阶段，引力波以大量形式产生，与简单的解析论证相比，这导致峰值频率发生偏移，光谱的整体幅度增加了$\mathcal{O}(100)$倍。 重要的是，我们还发现，发射的引力波的特征频率随着网络的衰变而增加，这导致高频光谱指数变软。 因此，这个高频光谱携带了与坍缩阶段动力学相关的关键信息，并且可以利用即将到来的数据来区分不同的畴壁场景。 显示英文摘要

摘要： Cosmological domain walls appear in many well-motivated extensions to the standard model of particle physics. If produced, they quickly enter into a self-similar scaling regime, where they are capable of efficiently sourcing a stochastic background of gravitational waves. In order to avoid a cosmological catastrophe, they must also decay before their enormous energy densities can have adverse effects on background dynamics. Here, we provide a suite of lattice simulations to comprehensively study the gravitational wave signatures of the domain wall network during this decay phase. The domain walls are initially formed through spontaneous breaking of a $\mathbb{Z}_2$ symmetry, and subsequently decay through the action of a small bias term which causes regions of false vacuum to collapse. We find that gravitational waves are produced in abundance throughout this collapsing phase, leading to a shift in the peak frequency and increase in the overall amplitude of the spectrum by an $\mathcal{O}(100)$ factor when compared against simple analytic arguments. Importantly, we also find that the characteristic frequency of emitted gravitational waves increases as the network decays, which leads to a softening of the high frequency spectral index. This high frequency spectrum therefore carries key information related to the dynamics of the collapsing phase, and can be used to discriminate between different domain wall scenarios using upcoming data.