AI 中文总结
该研究提出化学势匹配暗物质（$\mu$DM）新模型，通过匹配重子数化学势与暗物质质量解释重子-暗物质巧合，可产生 eV-keV 或经熵稀释至 MeV 质量的暗物质。
AI 中文摘要
对于相对论退耦的热残余物，暗物质的能量熵比满足$\rho_{\rm DM}/s\sim 10^{-3}m_{\rm DM}$，这是熟知的热暗物质丰度关系。在弱 sphaleron 冻结后，重子不对称可参数化为$\rho_{\rm baryon}/s\sim 10^{-4}|\mu_B|$，其中$\mu_B$为重子数化学势。我们提出一类名为化学势匹配暗物质（$\mu$DM）的新模型，令$|\mu_B|\sim m_{\rm DM}$，为重子-暗物质巧合提供新途径。作为$\mu$DM 的具体示例，我们考虑激发态构成暗物质的 Affleck-Dine 场，还简要讨论与类轴子粒子壁相关的自发电弱重子生成。在无熵稀释时，该巧合机制通常指向暗物质质量处于 eV-keV 范围；若热产生由玻色增强受激发射主导，其动量分布可呈冷态；若暗物质与重子产额确定后发生熵稀释，质量可提升至 MeV 量级。
英文摘要
For a relativistically decoupled thermal relic, the dark-matter energy-to-entropy ratio scales as $ρ_{\rm DM}/s\sim 10^{-3}m_{\rm DM}$. This is the familiar hot-dark-matter abundance relation. Immediately after weak-sphaleron freeze-out, the baryon asymmetry can be parametrized as $ρ_{\rm baryon}/s\sim 10^{-4}|μ_B|$. Here $μ_B$ is the baryon-number chemical potential. We propose a new class of models, called chemical-potential-matched dark matter ($μ$DM), in which $|μ_B|\sim m_{\rm DM}$, thereby providing a new route to the baryon-dark matter coincidence. As a concrete example of $μ$DM, we consider an Affleck-Dine field whose excitations constitute dark matter. We also briefly discuss spontaneous electroweak baryogenesis associated with axion-like-particle walls. In the absence of entropy dilution, this coincidence mechanism generically points to dark matter in the eV-keV mass range. Its momentum distribution can nevertheless be cold if thermal production is dominated by Bose-enhanced stimulated emission. Alternatively, entropy dilution after both the dark-matter and baryon yields are fixed allows masses up to the MeV scale.
Comments15 pages, 4figures, comments welcome!
