The NANOGrav collaboration has recently observed first evidence of a grav- itational wave background (GWB) in pulsar timing data. Here we explore the possibility that this GWB is due to new physics, and show that the signal can be well fit also with peaked spectra like the ones expected from phase transitions (PTs) or from the dynamics of axion like particles (ALPs) in the early universe. We find that a good fit to the data is obtained for a very strong PT at temperatures around 1 MeV to 10 MeV. For the ALP explanation the best fit is obtained for a decay constant of F ≈ 5 × 10^17 GeV and an axion mass of 2 × 10^−13 eV. We also illustrate the ability of PTAs to constrain the parameter space of these models, and obtain limits which are already comparable to other cosmological bounds.

中文翻译：

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从黑暗的侧面窃窃私语：用NANOGrav数据面对光的新物理

NANOGrav的合作最近在脉冲星定时数据中观察到了引力波背景（GWB）的初步证据。在这里，我们探讨了这种GWB可能是由于新物理学引起的，并表明该信号也可以很好地适应峰值频谱，例如从相变（PT）或轴心像粒子的动力学（ALP）预期的频谱。早期的宇宙。我们发现，在大约1 MeV至10 MeV的温度下获得非常强的PT，可以很好地拟合数据。对于ALP解释，对于衰减常数F≈5×10 ^ 17 GeV和轴突质量为2×10 ^ -13 eV，可以获得最佳拟合。我们还说明了PTA约束这些模型的参数空间并获得已经可以与其他宇宙学范围相媲美的极限的能力。