Gravitational wave spectra from oscillon formation after inflation
Gravitational wave spectra from oscillon formation after inflation
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DOI：
10.1007/jhep03(2021)021
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发表时间：
2020-11
影响因子：
5.4
通讯作者：
T. Hiramatsu;E. Sfakianakis;Masahide Yamaguchi
中科院分区：
文献类型：
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作者：
T. Hiramatsu;E. Sfakianakis;Masahide Yamaguchi
我们系统地研究了具有振荡支持潜力的单场膨胀的预热行为。我们计算发射的引力波的属性以及产生的振荡的数密度和特性。通过对各种电势类型进行数值模拟，我们将分析的电势分为两个系列，每个系列都包含具有不同大小场依赖性的电势。我们发现，无论确切的势形状如何，发射的引力波的频谱形状和振幅都具有普遍特征，在暴胀子振荡起始周期的物理波数 k/a∼ m 附近出现峰值。这可以作为确凿的证据来推断剧烈预热阶段的存在以及膨胀后可能形成的振荡。尽管存在这种明显的普遍性，但我们还发现这两个势能族之间发射的引力波频谱形状存在差异，从而导致它们之间存在区别特征。特别是，所有势均显示在引力波谱中出现了双峰结构，该双峰结构是在振荡形成时出现的。然而，表现出有效参数共振的势往往会抹掉这种结构，并且在模拟结束时，双峰结构被引力波谱中的一个宽峰取代。我们进一步计算每个潜在选择所产生的振荡的数密度和特性，发现稳定振荡和瞬态超密度的数密度和尺寸分布的差异。我们还执行线性波动分析，并使用相应的 Floquet 图将模拟结果与各种电位类型的参数共振结构联系起来。我们发现标量扰动的增长率和相关的振荡形成时间对势的小场形状敏感，而振荡的宏观物理性质（例如总数）取决于势的大场形状。
We systematically investigate the preheating behavior of single field inflation with an oscillon-supporting potential. We compute both the properties of the emitted gravitational waves as well as 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 of the spectrum and the amplitude of emitted gravitational waves have a universal feature with the peak around the physical wavenumber k/a∼ m at the inflaton oscillation starting 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 also find differences in the shape of the spectrum of emitted gravitational waves between the two families of potentials, leading to discriminating features between them. In particular, all potentials show the emergence of a two-peak structure in the gravitational wave spectrum, arising at the time of oscillon formation. However, potentials that exhibit efficient parametric resonance tend to smear out this structure and by the end of the simulation the two-peak structure is replaced by one broad peak in the GW spectrum. We further compute the number density and properties of the produced oscillons for each potential choice, finding differences in the number density and size distribution of stable oscillons and transient overdensities. We also perform a linear fluctuation analysis and use the corresponding Floquet charts to relate the results of our simulations to the structure of parametric resonance for the various potential types. We find that the growth rate of the scalar perturbations and the associated oscillon formation time are sensitive to the small-field shape of a potential while the macroscopic physical properties of oscillons such as the total number depend on the large-field shape of a potential.