Gravitational waves have become an irreplaceable tool for exploring the post-inflationary universe. Their cosmological and astrophysical origins have been attracting numerous attention. In this Letter, we point out a novel source of ultra-high frequency gravitational waves: the decay of particles produced during the reheating era. We highlight the decays of the inflaton and the Higgs bosons in the Standard Model and in the gauged B-L model as representative cases, showing how they yield a testable gravitational wave spectrum by future observations. We find that the peak frequency and the strain in the Higgs boson decay in the gauged B-L model, when the symmetry breaking scale is higher than the inflationary scale, can be greater than those in the inflaton decay scenario. Typically, the predicted spectrum lies beyond MHz in frequency and thus calls for non-interferometric experiments. Regardless of the shape of the spectrum, on the other hand, the total energy density of the produced gravitational waves can be reached by future Big Bang nucleosynthesis limits.

中文翻译：

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粒子在再加热过程中衰变的引力波


引力波已成为探索暴胀后宇宙不可替代的工具。它们的宇宙学和天体物理学起源引起了众多关注。在这封信中，我们指出了超高频引力波的一个新来源：再加热时代产生的粒子衰变。我们强调标准模型和计量 B-L 模型中暴胀子和希格斯玻色子的衰变作为代表性案例，展示它们如何通过未来的观测产生可测试的引力波谱。我们发现，当对称破缺尺度高于暴胀尺度时，计量 B-L 模型中希格斯玻色子衰变的峰值频率和应变可能大于暴胀衰变场景中的峰值频率和应变。通常，预测频谱的频率超出 MHz，因此需要进行非干涉实验。另一方面，无论光谱的形状如何，所产生的引力波的总能量密度都可以达到未来大爆炸核合成的极限。