The ALP miracle: unified inflaton and dark matter
The ALP miracle: unified inflaton and dark matter
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DOI：
10.1088/1475-7516/2017/05/044
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发表时间：
2017-02
影响因子：
6.4
通讯作者：
Ryuji Daido;F. Takahashi;W. Yin
中科院分区：
文献类型：
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作者：
Ryuji Daido;F. Takahashi;W. Yin
我们提出一种设想，即通过单一的类轴子粒子（ALP）以统一的方式描述通货膨胀（注：这里结合语境应为“暴胀”，宇宙学概念）和暗物质。在一类最简轴子山顶暴胀模型中，势能最大值和最小值处的有效质量大小相等但符号相反，因此类轴子暴胀子在暴胀期间和处于真真空态时质量都很轻。暴胀之后，大多数类轴子粒子通过与光子的耦合衰变成等离子体并消散，剩余的则成为暗物质。我们发现，观测到的宇宙微波背景（CMB）和物质功率谱以及暗物质丰度表明，类轴子粒子质量\(m_{\phi} = 𝒪(0.01)\)电子伏特，轴子 - 光子耦合\(g_{\phi \gamma \gamma} = 𝒪(10^{−11})\)吉电子伏特\(^{-1}\)：这就是类轴子奇迹。所建议的参数区域在下一代轴子太阳望远镜IAXO以及未来高强度激光实验的可及范围内。此外，热化的类轴子粒子对热暗物质有贡献，其丰度可用额外中微子种类的有效数量来表示，\(\Delta N_{eff} \approx 0.03\)，这可以通过未来的宇宙微波背景和重子声学振荡（BAO）观测进行检验。我们还讨论了存在多个类轴子粒子的情况，在早期宇宙中，与光子的耦合可以增强一个数量级或更多，这扩大了类轴子奇迹的参数空间。重类轴子粒子在混合暴胀中起到瀑布场的作用，并使宇宙再加热，并且可以在诸如SHiP等各种实验中进行搜寻。
We propose a scenario where both inflation and dark matter are described by a single axion-like particle (ALP) in a unified manner. In a class of the minimal axion hilltop inflation, the effective masses at the maximum and mimimum of the potential have equal magnitude but opposite sign, so that the ALP inflaton is light both during inflation and in the true vacuum. After inflation, most of the ALPs decay and evaporate into plasma through a coupling to photons, and the remaining ones become dark matter. We find that the observed CMB and matter power spectrum as well as the dark matter abundance point to an ALP of mass mϕ = 𝒪(0.01) eV and the axion-photon coupling gϕ γ γ = 𝒪(10−11) GeV−1: the ALP miracle. The suggested parameter region is within the reach of the next generation axion helioscope, IAXO, and high-intensity laser experiments in the future. Furthermore, thermalized ALPs contribute to hot dark matter and its abundance is given in terms of the effective number of extra neutrino species, Δ Neff ≃ 0.03, which can be tested by the future CMB and BAO observations. We also discuss a case with multiple ALPs, where the coupling to photons can be enhanced in the early Universe by an order of magnitude or more, which enlarges the parameter space for the ALP miracle. The heavy ALP plays a role of the waterfall field in hybrid inflation, and reheats the Universe, and it can be searched for in various experiments such as SHiP.