Axion-like fields heavier than about 10⁻²⁷ eV are expected to oscillate in the radiation dominated epoch when the Hubble parameter drops below their mass. Considering the Chern-Simons coupling with a dark gauge boson, large amount of dark photons are produced during a short time interval through tachyonic resonance instability. The produced dark photons then source gravitational tensor modes leading to chiral gravitational waves. Through this process, one can indirectly probe a large parameter space of coupled axion-dark photon models. In this work we first find an analytic expression for the number density of the dark photons produced during the tachyonic resonance regime. Second, by using the saddle point approximation we find an analytic expression for the gravitational wave spectrum in terms of the mass, coupling and misalignment angle. Our analytic results can be used for the observational analysis of these types of scenarios.

类轴力的场重约10 ^{− 27}当哈勃参数降至其质量以下时，预计eV将在辐射主导的时期内振荡。考虑到Chern-Simons与暗玻色子的耦合，在短时间间隔内，由于速激共振不稳定性会产生大量的暗光子。然后产生的暗光子发出引力张量模式，从而导致手性引力波。通过这一过程，可以间接探测耦合轴距-暗光子模型的较大参数空间。在这项工作中，我们首先找到在速激共振过程中产生的暗光子数密度的解析表达式。其次，通过使用鞍点逼近，我们可以从质量，耦合和偏心角的角度找到重力波谱的解析表达式。