We propose a novel mechanism to test time variation of the propagation speed of gravitational waves (GWs) in light of GWs astronomy. As the stochastic GWs experience the whole history of cosmic expansion, they encode potential observational evidence of such variation. We report that, one feature of a varying GWs speed is that the energy spectrum of GWs will present resonantly enhanced peaks if the GWs speed oscillates in time at high-energy scales. Such oscillatory behavior arises in a wide class of modified gravity theories. The amplitude of these peaks can be at reach by current and forthcoming GWs instruments, hence making the underlying theories falsifiable. This mechanism reveals that probing the variation of GWs speed can be a promising way to search for new physics beyond general relativity.

中文翻译：

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随机引力波背景的声速共振

我们提出了一种新颖的机制来根据GWs天文学测试引力波（GWs）传播速度的时间变化。由于随机GW经历了宇宙膨胀的整个历史，因此它们编码了这种变化的潜在观察证据。我们报告说，变化的GWs速度的一个特征是，如果GWs的速度在高能量范围内随时间振荡，则GWs的能谱将呈现共振增强的峰值。这种振荡行为出现在各种各样的改良重力理论中。当前和即将出现的GWs仪器都可以达到这些峰值的幅度，因此使基础理论无法成立。这种机制表明，探测GWs速度的变化可能是在广义相对论之外寻找新物理学的有前途的方法。