Dark matter comprised of axion-like particles (ALPs) generated by the realignment mechanism in the post-inflationary scenario leads to primordial isocurvature fluctuations. The power spectrum of these fluctuations is flat for small wave numbers, extending to scales accessible with cosmological surveys. We use the latest measurements of Cosmic Microwave Background (CMB) primary anisotropies together with CMB lensing, Baryonic Acoustic Oscillations (BAO) and Sunyaev Zel'dovich (SZ) cluster counts to measure the amplitude and tilt of the isocurvature component. We find preference for a white-noise isocurvature component in the CMB primary anisotropies; this conclusion is, however, weakened by current large-scale structure (LSS) data. Interpreting the result as a conservative upper limit on the isocurvature component, the combined bound on the ALP mass from all probes is $m_{a} \gtrsim 10^{-19}$ eV, with some dependence on how $m_{a}$ evolves with temperature. The expected sensitivity of cosmic shear and galaxy clustering from future LSS experiments and CMB lensing suggests improved bounds of $m_{a} \gtrsim 10^{-18}$-$10^{-13}$ eV, depending on scale cuts used to avoid non-linearities and the ALP mass-temperature dependence.

中文翻译：

---

面向CMB和大尺度结构的膨胀后轴子等曲率扰动

由在暴胀后情景中的重新排列机制产生的类轴子粒子 (ALP) 组成的暗物质导致原始等曲率波动。对于小波数，这些波动的功率谱是平坦的，扩展到宇宙学调查可达到的尺度。我们使用宇宙微波背景 (CMB) 初级各向异性的最新测量值以及 CMB 透镜、重子声学振荡 (BAO) 和 Sunyaev Zel'dovich (SZ) 簇计数来测量等曲率分量的幅度和倾斜度。我们发现在 CMB 主要各向异性中偏爱白噪声等曲率分量；然而，当前的大尺度结构 (LSS) 数据削弱了这一结论。将结果解释为等曲率分量的保守上限，来自所有探针的 ALP 质量的组合界限是 $m_{a} \gtrsim 10^{-19}$ eV，这与 $m_{a}$ 如何随温度变化有关。来自未来 LSS 实验和 CMB 透镜的宇宙剪切和星系团簇的预期灵敏度表明 $m_{a} \gtrsim 10^{-18}$-$10^{-13}$ eV 的改进范围，这取决于用于避免非线性和 ALP 质量-温度依赖性。