迈向统一的轴子宇宙学

中文摘要 AI 辅助

我们探索一种统一轴子框架，其将大统一理论、弦论启发的类轴子粒子（ALPs）与宇宙学相连接。从超对称SO(10)大统一理论（GUT）中与Peccei–Quinn对称性相关的QCD轴子出发，我们考虑由杂化弦论所启发的更广泛的超轻ALPs能谱。在该多轴子结构中，我们聚焦于宇宙学要求所选定的两个超轻能标：一个约10⁻²² eV的模式被假定为构成主导暗物质组分，可形成玻色-爱因斯坦凝聚体，其吸引性自相互作用会引发非线性坍缩，为高红移超大质量黑洞提供可能的种子；一个具有约10⁻²⁸ eV特征动力学能标的更轻本征方向可短暂增加复合前的膨胀速率并减小声视界。量级估算显示，解决哈勃张力问题需要声视界加权的轴子分数约为0.1，对应大初始位移时的有效衰变常数约为10¹⁸ GeV。我们证明，多轴子-多瞬子系统原则上可同时提供所需的对齐轻方向与高阶有效势，使10⁻²⁸ eV的贡献具有短暂性。该框架将理论上受启发的轴子自由度与暗物质、早期黑洞及哈勃张力现象学所需的不同能标相连接。

英文摘要

We explore a unified axion framework connecting grand unification, string-inspired axion-like particles (ALPs), and cosmology. Starting from the QCD axion associated with Peccei--Quinn symmetry in supersymmetric SO(10) GUT, we consider the broader spectrum of ultralight ALPs motivated by heterotic string theory. Within this multi-axion structure, we focus on two ultralight scales selected by cosmological requirements. A mode of order $10^{-22}$ eV is assumed to constitute the dominant dark-matter component and can form a Bose--Einstein condensate whose attractive self-interaction leads to nonlinear collapse, providing possible seeds for high-redshift supermassive black holes. A lighter eigen-direction with a characteristic dynamical scale of order $10^{-28}$ eV can transiently increase the pre-recombination expansion rate and reduce the sound horizon. An order-of-magnitude estimate shows that addressing the Hubble tension requires a sound-horizon-weighted axion fraction of order 0.1, corresponding, for a large initial displacement, to an effective decay constant of order $10^{18}$ GeV. We show that a multi-axion--multi-instanton system can in principle provide both the required aligned light direction and a higher-order effective potential that makes the $10^{-28}$ eV contribution transient. The framework links theoretically motivated axionic degrees of freedom to the distinct scales required by dark-matter, early-black-hole, and Hubble-tension phenomenology.

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18 pages, no figure