We present a novel UV freeze-in mechanism for enhancing the dark matter abundance in cosmologies where inflation is followed by an epoch dominated by a fluid stiffer than radiation. In such scenarios, even a small radiation abundance, produced for instance by instantaneous preheating effects, will eventually dominate the total energy density of the Universe without the need for a complete inflaton decay. For the sake of concreteness, we focus in non-oscillatory (NO) quintessential inflation models, albeit our treatment is rather general and can be extended to other scenarios. The high temperature of the initial thermal bath together with the absence of subsequent entropy injections into the Standard Model plasma translates into a highly-effective UV DM freeze-in. In particular, we find that, during kination, an enhancement in the DM abundance is generically obtained for any production cross-section not-decreasing with temperature.

中文翻译：

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促进 NO 模型中的紫外线冻结

我们提出了一种新的紫外线冻结机制，用于增强宇宙学中的暗物质丰度，其中膨胀之后是一个由比辐射更硬的流体主导的时代。在这种情况下，即使是由瞬时预热效应产生的少量辐射，最终也将主导宇宙的总能量密度，而无需完全的暴胀子衰变。为了具体起见，我们专注于非振荡 (NO) 典型的通货膨胀模型，尽管我们的处理方法相当笼统并且可以扩展到其他场景。初始热浴的高温以及随后没有熵注入标准模型等离子体转化为高效的 UV DM 冻结。特别是，我们发现，在连接过程中，