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arXiv 2008.12202astro-ph.COgr-qchep-th
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来自超慢滚和间断膨胀的PBH和次级GWs

PBHs and secondary GWs from ultra slow roll and punctuated inflation

H. V. Ragavendra, Pankaj Saha, L. Sriramkumar, Joseph Silk

摘要:

原始标量功率谱在大尺度上受到很好的约束,主要是通过观测宇宙微波背景(CMB)中的各向异性。在过去的几年里,人们已经认识到,在小尺度上功率的急剧上升将导致原始黑洞(PBH)的形成,并产生更高的次级引力波(GW),可能是可检测的振幅。很好地理解的是,标量功率谱具有CMB尺度上的COBE归一化幅度和较小尺度上的增强幅度,这是由于在暴胀的单个正则标量场模型中偏离慢滚而产生的。事实上,所谓的超慢滚膨胀的时代可以导致所需的放大。我们发现,导致超慢滚动的场景可以大致分为两种类型,一种是短暂偏离通货膨胀(称为间歇性通货膨胀的场景),另一种是不会出现这种偏离。我们考虑了一组单场暴胀模型,涉及规范标量场,导致超慢卷和间断的通货膨胀和检查的形成PBH以及在这些模型中产生的次级GWs。除了考虑特定的模型,我们重建潜力的第一个慢滚参数的某些功能选择,导致超慢滚和间断的通货膨胀,并调查其观测签名。除了二次张量功率谱,我们计算了二次张量双谱在等边极限在这些情况下。此外,我们还计算了在所有情况下出现的暴胀标量双谱,并讨论了标量非高斯性对PBH形成的程度和次级引力波振幅的影响。

英文摘要:

[Abridged] The primordial scalar power spectrum is well constrained on large scales, primarily by the observations of the anisotropies in the cosmic microwave background (CMB). Over the last few years, it has been recognized that a sharp rise in power on small scales will lead to enhanced formation of primordial black holes (PBHs) and also generate secondary gravitational waves (GWs) of higher and, possibly, detectable amplitudes. It is well understood that scalar power spectra with COBE normalized amplitude on the CMB scales and enhanced amplitudes on smaller scales can be generated due to deviations from slow roll in single, canonical scalar field models of inflation. In fact, an epoch of so-called ultra slow roll inflation can lead to the desired amplification. We find that scenarios that lead to ultra slow roll can be broadly classified into two types, one wherein there is a brief departure from inflation (a scenario referred to as punctuated inflation) and another wherein such a departure does not arise. We consider a set of single field inflationary models involving the canonical scalar field that lead to ultra slow roll and punctuated inflation and examine the formation of PBHs as well as the generation of secondary GWs in these models. Apart from considering specific models, we reconstruct potentials from certain functional choices of the first slow roll parameter leading to ultra slow roll and punctuated inflation and investigate their observational signatures. In addition to the secondary tensor power spectrum, we calculate the secondary tensor bispectrum in the equilateral limit in these scenarios. Moreover, we calculate the inflationary scalar bispectrum that arises in all the cases and discuss the imprints of the scalar non-Gaussianities on the extent of PBHs formed and the amplitude of the secondary GWs.

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