发表机构
Indiana University（印第安纳大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过贝叶斯分析NANOGrav 15年与EPTA DR2 New+数据集，发现后BBN物质和动能主导阶段的宇宙弦可解释PTA观测的纳赫兹引力波信号，且与标准宇宙学历史相比有显著证据。
AI 中文摘要
近期脉冲星计时阵列（PTA）观测报告了与随机引力波背景相符的共同低频信号证据。本研究探讨在大爆炸核合成（BBN）与复合之间的非标准宇宙学历史中，该信号的宇宙弦解释，该历史包含早期物质主导阶段后接动能阶段。此前研究表明，动能阶段可显著修改宇宙弦诱导的引力波谱，在纳赫兹范围产生特征性特征，并形成与当前PTA数据相符的形状。基于此，我们对NANOGrav 15年数据集与EPTA DR2 New+数据集分别进行贝叶斯分析，以量化数据支持此类宇宙学历史的程度。我们发现，在引力波信号的宇宙弦解释框架内，相较于标准宇宙学历史，物质与动能主导的短暂时期存在显著证据，来自NANOGrav 15年数据集的贝叶斯因子为3.63^{+0.22}_{-0.21}，同时推断的宇宙弦张力几乎未变。若超大质量黑洞双星（SMBHBs）的贡献较小（如天体物理学种群模拟所暗示），这一宇宙弦主导场景尤为相关。与引力波完全由SMBHBs产生的场景相比，在两种宇宙学历史及两个数据集下，含或不含额外SMBHBs贡献的宇宙弦解释均未表现出显著偏好。
英文摘要
Recent pulsar timing array (PTA) observations have reported evidence for a common low frequency signal consistent with a stochastic gravitational wave background. In this work, we investigate the cosmic string interpretation of this signal in a non-standard cosmological history between big bang nucleosynthesis and recombination, featuring an early matter-dominated era followed by a kination phase. Previous studies have shown that kination can significantly modify the cosmic-string-induced gravitational wave spectrum, generating characteristic features in the nanohertz range and producing a shape consistent with current PTA data. Building on this, we perform separate Bayesian analyses of the NANOGrav 15-year and EPTA DR2 New+ datasets to quantify the extent to which such a cosmological history is favored by the data. We find substantial evidence for a transient period of matter and kination domination over the standard cosmological history within a cosmic-string interpretation of the gravitational-wave signal, with a Bayes factor $3.63^{+0.22}_{-0.21}$ from the NANOGrav 15-year dataset, while leaving the inferred cosmic-string tension nearly unchanged. This cosmic-string-dominated scenario is particularly relevant if the contribution from supermassive black hole binaries (SMBHBs) is small, as hinted at by astrophysical population simulations. Compared with a scenario where gravitational waves are produced purely by SMBHBs, cosmic-string interpretations with and without an additional contribution from SMBHBs, across both expansion histories and datasets, reveal no significant preference.
Comments28 pages, 10 figures, and 8 tables
