论文标题
纳米格拉夫的含义对非标准宇宙学中原始引力波的影响
Implications of the NANOGrav result on primordial gravitational waves in nonstandard cosmologies
论文作者
论文摘要
最近，Nanograv协作报告了一个普通光谱随机过程的证据，这可能被解释为有史以来第一次检测随机引力波（GW）背景。我们讨论了非标准宇宙学历史上一阶GWS和二阶GW产生的信号的可能性。我们表明，可以通过非标准的热历史中的一阶GWS来解释纳米格拉夫的观察，而早期物质主导的时代可以解释标准宇宙学中的纳米格拉夫观察所需的参数空间，或者在非标准的基因统治时期被BBN和CMB的观察所排除。对于由大型原始标量波动产生的二阶GW，我们研究了标准辐射支配和两个特定的非标准情况，并具有几种形式的原始功率谱$P_ζ$（K）$，以实现丰富的原始黑洞（PBH）产生。我们发现，对于所有这些$P_ζ（K）$，可以用标准辐射统治来解释纳米格拉夫的观察。此外，一个类似灰尘的时期会导致$p_ζ$较低的振幅比辐射占主导的情况的幅度较低，并且仅在此处考虑的所有$p_ζ（k）$表格中仅符合Nanograv观测，在此处考虑的所有$p_ζ（k）$表格，在这里，峰值波数比Nananograv preavenumber范围更大。在这个非标准时期，对于广泛的功率谱，PBH在行星质量制度中的质量范围很广。如果要满足纳米格拉夫的结果，则非标准的Kination支配时代不能为$P_ζ（K）$中的任何一个产生足够的PBH。
Recently, the NANOGrav collaboration has reported evidence for a common-spectrum stochastic process, which might be interpreted as the first ever detection of stochastic gravitational wave (GW) background. We discuss the possibility of the signal arising from the first and second-order GWs in nonstandard cosmological history. We show that the NANOGrav observation can be explained by the first order GWs in the nonstandard thermal history with an early matter-dominated era, whereas the parameter space required to explain the NANOGrav observation in the standard cosmology or in the nonstandard epoch of kination domination is ruled out by the BBN and CMB observations. For the second-order GWs arising from the large primordial scalar fluctuations, we study the standard radiation domination and two specific nonstandard cases with a few forms of the primordial power spectrum $P_ζ(k)$ to achieve abundant primordial black hole (PBH) production. We find that the NANOGrav observation can be explained with standard radiation domination for all of these $P_ζ(k)$. Furthermore, a dustlike epoch leads to abundant PBH formation for a lower amplitude of $P_ζ(k)$ than the radiation dominated case and complies with the NANOGrav observation only for a few of the all $P_ζ(k)$ forms considered here, where the peak wavenumber is larger than the wavenumber range probed by the NANOGrav. In this nonstandard epoch, for a broad power spectrum, PBHs are produced in a wide mass range in the planetary mass regime. A nonstandard epoch of kination domination cannot produce enough PBH for any of the $P_ζ(k)$ if the NANOGrav result is to be satisfied.
