真空中引力波的衰减：量子化引力的低能效应
Gravitational waves decay in vacuum
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中文总结 AI 辅助
研究引力波在真空中衰变成光子这一量子过程，此过程经典和半经典下被禁且因引力子数平方增强。通过估算不同情况下衰减率，施加对宇宙学引力波源的限制，为探测引力波源提供新途径，源于引力场量子性质。
中文摘要 AI 辅助
经典引力波在真空中是稳定的。我们表明，若将其视为相干引力子态，它们会衰变成光子对，这是一个经典和半经典情况下都被禁止的量子过程，且会因引力子数平方\(N^2\)而增强。我们估算了致密双星和随机背景下的衰减率，包括受激衰减到宇宙微波背景的影响。在具有轻自由度的理论中，类似地衰变成这些轻自由度也是可能的，这对超轻暗物质更相关，因为它可能导致巨大的占据数。我们通过宇宙微波背景光谱畸变、河外背景和轻核光致裂变中光子的相应注入，首次对宇宙学引力波源施加了限制。总之，引力波衰变成光子为探测引力波源提供了一个新的（具有挑战性的）途径，其额外吸引人的特点是只有通过引力场的量子性质才有可能。
英文摘要
We show that gravitational waves (GW), treated as coherent graviton states, decay into photon pairs in vacuum. The process, even if suppressed by $G^2$, is lifted by two effects combined: the expected factor of the graviton number squared, $N^2$, and the coherence of the wave. We perform the calculation describing both gravity and the photons as quantized fields, though we show that the effect admits a semiclassical description once the metric is solved to second order. We estimate the resulting rates for compact binaries and a stochastic background, including the effect from stimulated decay to the cosmic microwave background (CMB). In theories with light degrees of freedom, an analogous decay into them is also possible, and more relevant for ultralight dark matter, as it can entail huge occupation numbers. We derive first constraints on cosmological GW sources by the corresponding injection of photons from CMB spectral distortions, extragalactic backgrounds, and light-nuclei photofission. In summary, the decay of GWs into photons offers a new (challenging) handle on the detection of GW sources, and represents a new mechanism to generate other particles across cosmic history.
