In this paper, we consider dynamical Chern-Simons gravity with the identification of the scalar field coupled though the Pontryagin density with the axion dark matter, and we discuss the effects of the parametric resonance on gravitational waves (GWs). When we consider GWs in a coherently oscillating axion cloud, we confirm that significant resonant amplification of GWs occurs in a narrow frequency band, and the amplification is restricted to the late epoch after the passage of the incident waves. We also identify the condition that an axion cloud spontaneously emits GWs. Once we take into account the randomness of the spatial phase distribution of the axion oscillations, we find that the amplification is suppressed compared with the coherent case, but significant amplification of GWs can still occur. We also examine whether or not the amplification of GWs is possible in the present universe, taking into account the history of the universe. We find that resonant amplification is difficult to be tested from GW observations in the standard scenario of the axion DM model, in which the axion is the dominant component of DM. However, there is some parameter window in which the resonant amplification of GWs might be observed, if the axion is subdominant component of DM, and the axion cloud formation is delayed until the Hubble rate becomes much smaller than the axion mass.

中文翻译：

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动力学陈-西蒙斯轴引力中的共振引力波

在本文中，我们通过识别通过庞特里亚金密度与轴子暗物质耦合的标量场来考虑动力学陈-西蒙斯引力，并讨论参数共振对引力波 (GW) 的影响。当我们考虑相干振荡轴子云中的 GW 时，我们确认 GW 的显着共振放大发生在窄频带内，并且放大仅限于入射波通过后的后期。我们还确定了轴子云自发发射 GW 的条件。一旦我们考虑到轴子振荡的空间相位分布的随机性，我们发现与相干情况相比放大被抑制，但仍然会发生显着的 GW 放大。考虑到宇宙的历史，我们还研究了当前宇宙中GWs的放大是否可能。我们发现，在轴子 DM 模型的标准场景中，很难从 GW 观测中测试共振放大，其中轴子是 DM 的主要组成部分。然而，如果轴子是 DM 的次主导成分，并且轴子云的形成被延迟，直到哈勃速率变得远小于轴子质量，那么在某些参数窗口中可能会观察到 GW 的共振放大。