标量诱导引力波在二阶以外的红外普适性
Infrared Universality of Scalar Induced Gravitational Waves Beyond Second Order
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中文总结 AI 辅助
本研究揭示了标量诱导引力波红外标度在任意阶微扰及非高斯性下的普适性，源于声波慢拍频持续驱动长波张量扰动，为探测宇宙物态方程提供稳健探针。
中文摘要 AI 辅助
原初黑洞暗物质是由增强的原初密度涨落坍缩形成的。原初黑洞的形成伴随着标量诱导引力波，其红外标度在领头阶仅依赖于背景的物态方程 $w$。确定这一特征标度在任意微扰阶修正下（包括存在非高斯性时）是否保持稳健，需要对红外标度的物理理解。在这项工作中，我们提供了这样的物理解释。我们发现，频率几乎相等的声波应力会产生缓慢的拍频。尽管入射波快速振荡，这种缓慢的拍频在其进入视界之前持续为长波长张量扰动提供源，从而产生仅依赖于膨胀背景的红外标度。我们证明，高阶相互作用产生自由传播的波，这些波最终在视界深处导致相同的缓慢拍频。由于非高斯性不会改变自由传播波的速度，因此它们不会修改红外标度。由于具有缓慢拍频的源在红外张量模式进入视界之前有足够的时间累积，它记录了背景膨胀，因此红外标度可以作为宇宙学物态方程的稳健探针。
英文摘要
Primordial black hole dark matter is formed from the collapse of enhanced primordial density fluctuations. The formation of primordial black holes is accompanied by scalar induced gravitational waves whose infrared scaling only depends on the equation of state, $w$, of the background at leading order. Establishing whether this characteristic scaling remains robust under corrections of arbitrary perturbative order, including in the presence of non-Gaussianities, requires a physical understanding of the infrared scaling. In this work, we provide such a physical interpretation. We find that the stress of sound waves with nearly equal frequencies produces a slow beat. Although the incoming waves oscillate rapidly, this slow beat continues to source the long wavelength tensor perturbation before its horizon entry, thus generating an infrared scaling that only depends on the expanding background. We show that higher order interactions generate freely propagating waves that finally lead to the same slow beat deep inside the horizon. Since non-Gaussianities would not change the speed of the freely propagating waves, they do not modify the infrared scaling. As the source with a slow beat has enough time to accumulate before the horizon entry of the infrared tensor mode, it records the background expansion and thus the infrared scaling could provide a robust probe of the cosmological equation of state.
发表机构
- Department of Physics, College of Sciences, Shanghai University（上海大学理学院物理系）
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