We present a scenario that ameliorates the tuning problems present in models of primordial black hole dark matter from inflation. Our setup employs the advantages of gravitational collapse in a long epoch of early matter domination with reheating temperature $\lesssim 10^{6}~\text{GeV}$. Furthermore, we make use of a string-inspired class of models where the inflaton is identified with a non-compact axion field. In this framework, the presence of multiple local minima in the inflaton potential can be traced back to an approximate discrete shift symmetry. This scenario allows the formation of primordial black holes in the observationally viable range of masses ($M_{\text{PBH}}\sim 10^{-13}M_{\odot}-10^{-16}M_{\odot}$) accounting for all dark matter, and in excellent agreement with the CMB. Crucially, we find a significant reduction in the required tuning of the parameters of the inflationary potential, in contrast to the standard case of primordial black hole formation during radiation domination.

中文翻译：

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用早期物质支配和轴子单调失调原始黑洞暗物质

我们提出了一种改善原始黑洞暗物质模型中存在的调谐问题的场景。我们的设置利用了在重新加热温度 $\lesssim 10^{6}~\text{GeV}$ 的早期物质统治的漫长时期中引力坍缩的优势。此外，我们使用受字符串启发的模型类，其中暴胀子被识别为非紧凑轴子场。在这个框架中，暴胀子势中多个局部最小值的存在可以追溯到近似的离散位移对称性。这种情况允许在观测可行的质量范围内形成原始黑洞 ($M_{\text{PBH}}\sim 10^{-13}M_{\odot}-10^{-16}M_{\odot }$) 解释了所有暗物质，并且与 CMB 非常一致。至关重要的是，