发表机构
University at Buffalo, The State University of New York; Fermi National Accelerator Laboratory; Space Telescope Science Institute; Johns Hopkins University（纽约州立大学布法罗分校; 费米国家加速器实验室; 太空望远镜科学研究所; 约翰斯·霍普金斯大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文构建均匀多轴子宇宙学模型，包含核合成瞬态、两个早期暗能量及晚时解冻场，数值求解其演化，并展示各时代能量分数及对额外轴子尺度的约束潜力。
AI 中文摘要
如果暗能量在宇宙历史中反复出现会怎样？在这种图景下，标量场暗能量的片段成为宇宙演化中不那么令人惊讶、更自然的特征。我们构建了一个均匀的多轴子宇宙学模型，其中包含大爆炸核合成期间的瞬态贡献、再复合之前的两个早期暗能量组分，以及一个提供当前暗能量密度的解冻场。随着哈勃摩擦减弱，这些场在由其势曲率尺度设定的相继时代开始滚动。它们的初始位移影响滚动延迟和峰值能量分数。瞬态场具有三次方余弦势，其六次方极小值允许在快速、小振幅振荡期间比辐射更快地稀释。所有四个场在共同的弗里德曼背景中演化，其首次滚动及后续动力学通过数值方法求解。参考普朗克2018的物质和辐射密度，基准模型在$z=10^9$附近具有约$0.99\%$的核合成时代峰值分数。两个早期暗能量场分别在$z=7.9\ imes10^3$和$2.4\ imes10^3$附近达到峰值，单个分数为$8.6\%$和$7.8\%$；它们的组合分数达到$9.7\%$。晚时场被归一化以提供约$0.685$的当前分数，而三个瞬态场留下约$6.0\ imes10^{-7}$的组合分数。一个对齐的双轴子例子说明了可用于暴胀扩展的增强场范围。我们还概述了如何通过搜索其他时代膨胀速率的瞬态贡献来约束额外的轴子尺度。
英文摘要
What if dark energy is recurrent throughout cosmic history? In this picture, episodes of scalar-field dark energy become less surprising and more natural features of cosmic evolution. We construct a homogeneous multi-axion cosmology with a transient contribution during Big Bang nucleosynthesis, two early dark energy components before recombination, and a thawing field that supplies the present dark-energy density. As Hubble friction weakens, the fields begin to roll at successive epochs set by their potential-curvature scales. Their initial displacements affect the rolling delays and peak energy fractions. The transient fields have third-power cosine potentials, whose sextic minima allow faster-than-radiation dilution during rapid, small-amplitude oscillations. All four fields are evolved in a common Friedmann background, with their first roll and subsequent dynamics resolved numerically. With reference matter and radiation densities taken from Planck 2018, the benchmark has a nucleosynthesis-era peak fraction of approximately $0.99\%$ near $z=10^9$. The two early dark energy fields peak near $z=7.9\times10^3$ and $2.4\times10^3$, with individual fractions of $8.6\%$ and $7.8\%$; their combined fraction reaches $9.7\%$. The late-time field is normalized to supply a present fraction of approximately $0.685$, while the three transients leave a combined fraction of approximately $6.0\times10^{-7}$. An aligned two-axion example illustrates the enhanced field range available for an inflationary extension. We also outline how searches for transient contributions to the expansion rate at other epochs could constrain additional axion scales.
Comments25+12 pages including appendix and references, 5 figures, 4 tables
