标题： 重温原初引力波的紫外尾 显示英文标题

标题： Revisiting the Ultraviolet Tail of the Primordial Gravitational Wave

摘要： 高频率的原初引力波（PGWs）具有比膨胀结束时哈勃参数更大的波数，这些波源自紫外（UV）模态，而这些模态从未超出视界。 这种PGW能量谱的UV尾部存在虚假的对数发散。 我们研究了这种发散的起源，并发现它来自瞬间的从膨胀到后膨胀的转变，这一转变可以通过考虑有限持续时间来消除。 首次，我们得到了PGW能量谱的半解析表达式。 我们发现UV尾部呈指数衰减，而衰减率仅取决于转变速率。 当存在一个刚性的后膨胀阶段时，增强的PGW表现出幂律增加和指数衰减的特征光谱形状。 我们提出了一种拟合公式，可用于信号搜索。 显示英文摘要

摘要： High-frequency primordial gravitational waves (PGWs) with wave numbers larger than the Hubble parameter at the end of inflation are originated from the ultraviolet (UV) modes, which are never stretched out of the horizon. Such a UV tail of the PGW energy spectrum has a spurious logarithmic divergence. We study the origin of such a divergence, and find that it comes from the instantaneous inflation-to-post-inflation transition, which can be removed by considering a finite duration. For the first time, we obtain a semi-analytical expression for the PGW energy spectrum. We find that the UV tail decays exponentially, while the decay rate depends solely on the transition rate. When there is a stiff post-inflationary stage, the enhanced PGW displays a characteristic spectral shape of power-law increasing and exponential decaying. We propose a fitting formula which can be used for signal searching.