AI 中文总结
该研究发现宇宙学一阶相变的真真空泡膨胀可大量产生标量粒子和轴子，其机制参数上主导弱耦合粒子的其他产生过程，为暗辐射和暗物质提供新来源。
AI 中文摘要
我们重新研究了宇宙学一阶相变过程中的粒子产生问题，发现真真空泡的膨胀可以成为粒子产生的丰富来源。具体而言，对于与泡轮廓线性耦合的大质量自旋0场，即使以恒定径向速度膨胀的球形泡也能有效产生粒子，直到泡壁的局部静止系曲率半径超过粒子的康普顿波长——这与“以恒定速度运动的壁无法辐射”的预期相反。我们针对加速和恒定速度膨胀历史计算了所产生粒子的动量谱，确定了相干产生和非相干产生的区域，量化了微扰处理的有效性，并表明该机制在参数上可以主导弱耦合粒子的其他产生过程，包括“冻入（freeze-in）”过程。我们的结果适用于文献中研究的许多轻量弱耦合粒子模型，为暗辐射和暗物质提供了新的来源。特别地，隐藏杨-米尔斯部分的一阶退禁闭-禁闭相变可以大量产生类轴子粒子，在大部分参数空间内产生暗辐射和/或暗物质的特征信号。
英文摘要
We revisit aspects of particle production during cosmological first-order phase transitions, and show that the expansion of true-vacuum bubbles can be a copious source of particle production. Specifically, for a massive spin-0 field linearly coupled to the bubble profile, spherical bubbles expanding even at \emph{constant} radial velocity efficiently produce particles until the local-rest-frame radius of curvature of the bubble wall exceeds the particle Compton wavelength -- contrary to the expectation that walls moving at constant speed cannot radiate. We compute the momentum spectrum of the produced particles for both accelerated and constant-velocity expansion histories, identify the regimes of coherent and incoherent production, quantify the validity of the perturbative treatment, and show that this mechanism can parametrically dominate other production processes of feebly coupled particles, including freeze-in. Our results apply to many models of light, feebly coupled particles studied in the literature, providing new sources of dark radiation and dark matter. In particular, a first-order deconfinement-confinement transition in a hidden Yang-Mills sector can abundantly produce axion-like particles, leading to dark radiation and/or dark matter signatures over large regions of parameter space.
Comments36 pages, 8 figures
