A well-known route to form primordial black holes in the early universe relies on the existence of unusually large primordial curvature fluctuations, confined to a narrow range of wavelengths that would be too small to be constrained by Cosmic Microwave Background (CMB) anisotropies. This scenario would however boost the generation of μ-type spectral distortions in the CMB due to an enhanced dissipation of acoustic waves. Previous studies of μ-distortion bounds on the primordial spectrum were based on the assumptions of Gaussian primordial fluctuations. In this work, we push the calculation of μ-distortions to one higher order in photon anisotropies. We discuss how to derive bounds on primordial spectrum peaks obeying non-Gaussian statistics under the assumption of local (perturbative or not) non-Gaussianity. We find that, depending on the value of the peak scale, the bounds may either remain stable or get tighter by several orders of magnitude, but only when the departure from Gaussian statistics is very strong. Our results are translated in terms of bounds on primordial supermassive black hole mass in a companion paper.

中文翻译：

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非高斯（或非高斯）扰动引起的声耗散引起的频谱失真


在早期宇宙中形成原初黑洞的一条众所周知的途径依赖于异常大的原初曲率涨落的存在，该涨落仅限于狭窄的波长范围，该范围太小而无法受到宇宙微波背景（CMB）各向异性的限制。然而，这种情况将促进μ由于声波耗散增强而导致 CMB 中的 型频谱失真。以前的研究μ原初光谱的畸变界限基于高斯原初涨落的假设。在这项工作中，我们推动计算μ -光子各向异性扭曲到一个更高阶。我们讨论如何在局部（微扰或非微扰）非高斯性的假设下推导出服从非高斯统计的原始谱峰的界限。我们发现，根据峰值尺度的值，界限可能会保持稳定或变得更紧几个数量级，但前提是与高斯统计的偏差非常大。我们的结果在另一篇论文中被转化为原始超大质量黑洞质量的界限。