论文标题
PBH和次级GWS可以起源于挤压的初始状态吗？
Could PBHs and secondary GWs have originated from squeezed initial states?
论文作者
论文摘要
[删节]最近，由于小尺度上的标量功率增强，原始黑洞（PBHS）和次级重力波（GWS）的产生在文献中引起了很大的关注。通常，被认为达到这种增强功率的机制涉及对标准慢速通货膨胀动力学的修改，这些动态借助微调电位实现。在这项工作中，我们研究了在功率谱中生成特征的另一种众所周知的方法，其中假定扰动的初始状态被挤压状态。从技术上讲，这种方法可以直接实现，因为可以从功率谱的所需形式确定挤压初始状态的Bogoliubov系数。众所周知，对于挤压的初始状态，标量双光谱是很强的依赖性的，并且违反了挤压限制中标量双光谱的一致性条件。实际上，非高斯参数$ f _ {_ {\ rm nl}} $表征标量bispectrum的表征被证明与挤压模式成反比，并且这种依赖性在大波浪数量上增强了其在大波浪中的振幅，即使从标准堆式束 - 戴维型型号的vacumiative则高度敏感。这些方面可能有助于导致PBH的形成增强和次要GWS的产生。但是，我们发现：（i）从动力学机制中挤压的初始状态的所需形式可能具有挑战性，并且（ii）由于激发态引起的反应严重限制了与大波浪数量上束束真空的偏差程度。我们认为，除非避开反应问题，否则挤压的初始状态不能导致小尺度上的力量大幅增加，这是增强PBHS形成和次要GWS所需的。
[Abridged] Recently, the production of primordial black holes (PBHs) and secondary gravitational waves (GWs) due to enhanced scalar power on small scales have garnered considerable attention in the literature. Often, the mechanism considered to arrive at such enhanced power involves a modification of the standard slow roll inflationary dynamics, achieved with the aid of fine-tuned potentials. In this work, we investigate another well known method to generate features in the power spectrum wherein the initial state of the perturbations is assumed to be squeezed states. This approach is technically straightforward to implement since the Bogoliubov coefficients characterizing the squeezed initial states, can be immediately determined from the desired form of the power spectrum. It is known that, for squeezed initial states, the scalar bispectrum is strongly scale dependent and the consistency condition governing the scalar bispectrum in the squeezed limit is violated. In fact, the non-Gaussianity parameter $f_{_{\rm NL}}$ characterizing the scalar bispectrum proves to be inversely proportional to the squeezed mode and this dependence enhances its amplitude at large wave numbers making it highly sensitive to even a small deviation from the standard Bunch-Davies vacuum. These aspects can possibly aid in leading to enhanced formation of PBHs and generation of secondary GWs. However, we find that: (i) the desired form of the squeezed initial states may be challenging to achieve from a dynamical mechanism, and (ii) the backreaction due to the excited states severely limits the extent of deviation from the Bunch-Davies vacuum at large wave numbers. We argue that, unless the issue of backreaction is circumvented, squeezed initial states cannot lead to a substantial increase in power on small scales that is required for enhanced formation of PBHs and generation of secondary GWs.
