We make forecasts for the impact a future “midband” space-based gravitational wave experiment, most sensitive to ${10}^{-2}-10\mathrm{Hz}$, could have on potential detections of cosmological stochastic gravitational wave backgrounds (SGWBs). Specific proposed midband experiments considered are TianGo, B-DECIGO, and AEDGE. We propose a combined power-law integrated sensitivity (CPLS) curve combining GW experiments over different frequency bands, which shows the midband improves sensitivity to SGWBs by up to two orders of magnitude at ${10}^{-2}-10\mathrm{Hz}$. We consider GW emission from cosmic strings and phase transitions as benchmark examples of cosmological SGWBs. We explicitly model various astrophysical SGWB sources, most importantly from unresolved black hole mergers. Using Markov Chain Monte Carlo, we demonstrated that midband experiments can, when combined with LIGO $\mathrm{A}+$ and LISA, significantly improve sensitivities to cosmological SGWBs and better separate them from astrophysical SGWBs. In particular, we forecast that a midband experiment improves sensitivity to cosmic string tension $G\mu$ by up to a factor of 10, driven by improved component separation from astrophysical sources. For phase transitions, a midband experiment can detect signals peaking at 0.1–1 Hz, which for our fiducial model corresponds to early Universe temperatures of $T_{*}\sim {10}^4–{10}^6\mathrm{GeV}$, generally beyond the reach of LIGO and LISA. The midband closes an energy gap and better captures characteristic spectral shape information. It thus substantially improves measurement of the properties of phase transitions at lower energies of $T_{*}\sim O({10}^3)\mathrm{GeV}$, potentially relevant to new physics at the electroweak scale, whereas in this energy range LISA alone will detect an excess but not effectively measure the phase transition parameters. Our modeling code and chains are publicly available.

中文翻译：

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中频引力波实验对宇宙学随机引力波背景可探测性的影响

我们对未来的“中频”天基引力波实验的影响做出预测，最敏感的是 ${10}^{-2}-10\mathrm{赫兹}$, 可能对宇宙学随机引力波背景 (SGWB) 进行潜在检测。考虑的具体提议的中频实验是 TianGo、B-DECIGO 和 AEDGE。我们提出了一种结合不同频带上的 GW 实验的组合幂律积分灵敏度 (CPLS) 曲线，这表明中频带将 SGWB 的灵敏度提高了两个数量级${10}^{-2}-10\mathrm{赫兹}$. 我们将宇宙弦和相变的 GW 发射视为宇宙学 SGWB 的基准示例。我们明确地模拟了各种天体物理 SGWB 源，最重要的是来自未解决的黑洞合并。使用马尔可夫链蒙特卡罗，我们证明了中频实验与 LIGO 结合时可以$\mathrm{一种}+$和 LISA，显着提高了对宇宙学 SGWB 的敏感性，并更好地将它们与天体物理 SGWB 区分开来。特别是，我们预测中频实验会提高对宇宙弦张力的敏感性$G\mu$由于与天体物理来源的组件分离得到改进，最多可提高 10 倍。对于相变，中频实验可以检测到 0.1-1 Hz 的峰值信号，对于我们的基准模型，这对应于早期宇宙温度${吨}_{*}～{10}^4\mathrm{——}{10}^6\mathrm{电子伏特}$，一般超出 LIGO 和 LISA 的能力范围。中频带关闭能隙并更好地捕获特征光谱形状信息。因此，它大大改善了在较低能量下相变特性的测量${吨}_{*}～哦({10}^3)\mathrm{电子伏特}$，可能与电弱尺度的新物理学相关，而在这个能量范围内，LISA 单独会检测到过量但不能有效地测量相变参数。我们的建模代码和链是公开的。