来自超哈勃气泡的引力波
Gravitational waves from super-Hubble bubbles
AI总结：
研究宇宙学一阶相变中暴胀后超哈勃气泡碰撞产生的引力波，发现其峰值频率可能低于兆赫兹，振幅增强，有望处于LIGO、NANOGrav、LISA等实验的可观测范围内，通过简单模型予以证明。
AI中文摘要：
我们考虑一种宇宙学一阶相变，其中真空气泡在暴胀期间成核，但直到宇宙进入辐射主导时代才碰撞并渗透。如果碰撞在暴胀结束后不久发生，这些气泡的大小可能会显著大于哈勃长度。这对气泡碰撞产生的引力波有两个重要影响：首先，由于峰值频率由共动气泡半径决定，它可能远低于暴胀末期气泡碰撞典型的兆赫兹频率。其次，当比较同时开始的碰撞时，相对于哈勃大小及更小的气泡，引力波的振幅会大大增强。这两种效应共同意味着，暴胀结束后不久由超哈勃气泡产生的引力波可能处于LIGO和NANOGrav以及LISA和其他未来引力波实验的可观测频率和振幅范围内。我们用一个简单的示例模型证明了这一点。
英文摘要：
We consider a cosmological first-order phase transition in which bubbles of true vacuum nucleate during inflation but do not collide and percolate until the Universe has entered the radiation-dominated era. If the collisions take place soon after the end of inflation, the size of these bubbles can be significantly greater than the Hubble length. This has two important consequences for the gravitational waves produced by the bubble collisions: First, as the peak frequency is determined by the comoving bubble radius, it can be well below the MHz frequencies typical for bubble collisions at the end of inflation. Second, when comparing collisions beginning at the same time, the amplitude of the gravitational waves is greatly enhanced relative to Hubble-sized and smaller bubbles. Together, these two effects mean that gravitational waves produced by super-Hubble bubbles soon after the end of inflation can be within the observable frequency and amplitude ranges of LIGO and NANOGrav, as well as LISA and other future gravitational wave experiments. We demonstrate this with a simple illustrative model.
