轴子多重态模型：暴胀与暗物质
A multi-axion model of inflation and dark matter
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中文总结 AI 辅助
该研究提出额外维度产生的轴子多重态模型，以单个暴胀子驱动暴胀且符合观测约束，同时轻态作为暗物质，满足稳定性与丰度要求，统一解释暴胀与暗物质起源。
中文摘要 AI 辅助
额外维度模型包含大量重态，这些态不可避免地会对宇宙学动力学产生贡献。具体而言，紧致化后，高维轴子会产生一系列态，这些态在早期展现暴胀特性，在后期则表现为动力学暗物质。有趣的是，参数的自然选择意味着场空间中的暴胀轨迹近似为测地线，即暴胀实际上由对应最重态的单个暴胀子驱动。在此情景下，所有暴胀可观测量（包括产生的谱畸变）均符合当前观测约束，运动方程的精确数值解显示，再加热过程可一致地进行至几MeV的温度。此外，所有轻于暴胀子的态仅在物质主导时期开始主导宇宙的能量密度，因此在后期表现为暗物质。这些态会经历级联衰变成为辐射，同时保持足够的暗物质丰度以解释观测到的 relic密度。最轻的暗物质候选体在远超宇宙年龄的时间尺度上保持稳定，因此甚至满足最保守的观测约束。
英文摘要
Models with extra dimensions include a tower of massive states that unavoidably contribute to cosmological dynamics. In particular, after compactification, a higher-dimensional axion gives rise to a set of states whose dynamics at early times exhibit the properties of inflation and, at late times, those of dynamical dark matter. Interestingly, natural choices of parameters imply that the inflationary trajectory in field space is approximately geodesic, meaning that inflation is effectively driven by a single inflaton corresponding to the heaviest state. In this scenario, all inflationary observables, including the emerging spectral distortions, are consistent with current observational constraints, and exact numerical solutions of the equations of motion show that reheating can consistently proceed down to temperatures of a few MeV. Furthermore, all states lighter than the inflaton only come to dominate the energy density of the Universe during the matter-dominated era, thus behaving as dark matter at late times. These states undergo a cascade of decays into radiation, while maintaining a sufficient dark-matter abundance to account for the observed relic density. The lightest dark-matter candidate remains stable on timescales far exceeding the age of the Universe, thereby satisfying even the most conservative observational constraints.
