We study the visible photon production from the viscous dissipation of the dark matter (DM) fluid. The visible photon production depends on the magnitude of the dark matter viscosity and becomes important at the late times. We argue that for sufficiently large dark matter viscosity, the number of the resonantly converted visible photons becomes large which populates the Rayleigh-Jeans (RJ) tails of the Cosmic Microwave Background (CMB) radiation. Consequently, these excess visible photons possibly can explain the reported EDGES anomaly in the 21 cm signal. Further, we explore the parameter space for which the 21 cm signal can provide the region to probe the dark radiation and the DM viscosity.

中文翻译：

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从暗物质的粘度和EDGES异常的解释中减轻暗物质

我们研究了暗物质 (DM) 流体的粘性耗散产生的可见光子。可见光子的产生取决于暗物质粘度的大小，并且在后期变得重要。我们认为，对于足够大的暗物质粘度，共振转换的可见光子的数量会变大，从而填充宇宙微波背景 (CMB) 辐射的瑞利-牛仔裤 (RJ) 尾。因此，这些多余的可见光子可能可以解释 21 厘米信号中报告的边缘异常。此外，我们探索了 21 cm 信号可以提供探测暗辐射和 DM 粘度的区域的参数空间。