标题： 轴子暗物质高尺度暴胀的随机等曲率约束 显示英文标题

标题： Stochastic isocurvature constraints for axion dark matter with high-scale inflation

摘要： 轴子是暗物质候选者中最有说服力的之一。 它们通过真空错位机制在早期宇宙中产生，导致等曲率扰动，这些扰动受到宇宙微波背景测量的限制。 在本文中，我们使用随机斯塔罗宾斯基-横山形式的谱展开来计算轴子等曲率功率谱，该方法捕捉了轴子动力学中的非线性效应。 与大多数现有文献不同，我们关注高暴胀哈勃速率，约为$10^{13}~{\rm GeV}$，并证明在这一范围内，轴子可以解释全部或部分暗物质丰度，而不会违反等曲率约束或张量模式约束。 关键的是，我们发现在这个范围的大部分区域，等曲率谱主要由非微扰贡献主导。 因此，在这个区域，常用的线性近似不可靠，使得随机方法变得至关重要。 显示英文摘要

摘要： Axions are among the best motivated dark matter candidates. Their production in the early Universe by the vacuum misalignment mechanism gives rise to isocurvature perturbations, which are constrained by cosmic microwave background measurements. In this paper, we compute the axion isocurvature power spectrum using spectral expansion in the stochastic Starobinsky-Yokoyama formalism, which captures non-linear effects in the axion dynamics. In contrast to most of the existing literature, we focus on high inflationary Hubble rates of order $10^{13}~{\rm GeV}$, and demonstrate that there is a significant window in which axions can account for all or part of the dark matter abundance without violating the isocurvature bounds or tensor mode bounds. Crucially, we find that the isocurvature spectrum is dominated by non-perturbative contributions in a large part of this window. Therefore the commonly used linear approximation is not reliable in this region, making the stochastic approach essential.