论文标题
长期以来一直生活在快速扩展的宇宙中及其在宇宙微波背景上的烙印
Long lived inert Higgs in fast expanding universe and its imprint on cosmic microwave background
论文作者
论文摘要
在宇宙微波背景形成时，存在任何额外的辐射能密度，都可以显着影响测量有效的相对论中微子自由度或$ {\rmΔn_{eff}} $，这是通过普朗克协作非常精确地衡量的。在这里，我们提出了一个场景，即长期存在的惰性标量（非常弱耦合到黑暗扇形），通过冷冻机制加上速度的暗物质加上标准模型中微子在非常低的温度$（t <t _ {\ rm bbn}）下衰减。我们在快速扩展的宇宙中探索了这个模型，假定宇宙的早期时代$（t> t _ {\ rm bbn}）$由非标准的物种$φ$而不是标准辐射主导。在这种非标准的宇宙学图中，惰性标量的这种晚期衰减可以在将其从热浴中解散后中微子扇区的某些熵，这将为$ {\rmδ{n_ {eff}}} $带来可观的贡献。此外，在这种情况下，对$Δn_ {\ rm eff} $的新贡献与暗物质部门高度相关。因此，可以通过使用电流（Planck2018）和即将出版的（CMB-S4 \＆SPT3G）实验来精确测量$Δn_ {\ rm eff} $，可以通过精确测量$Δn_{\ rm eff} $来探索这种微弱的暗物质颗粒（FIMP）。
Presence of any extra radiation energy density at the time of cosmic microwave background formation can significantly impact the measurement of the effective relativistic neutrino degrees of freedom or ${\rm ΔN_{eff}}$ which is very precisely measured by the Planck collaboration. Here, we propose a scenario where a long lived inert scalar, which is very weakly coupled to dark sector, decays to a fermion dark matter via freeze-in mechanism plus standard model neutrinos at very low temperature $(T< T_{\rm BBN})$. We explore this model in the fast expanding universe, where it is assumed that the early epoch $(T > T_{\rm BBN})$ of the universe is dominated by a non-standard species $Φ$ instead of the standard radiation. In this non-standard cosmological picture, such late time decay of the inert scalar can inject some entropy to the neutrino sector after it decouples from the thermal bath and this will make substantial contribution to ${\rm Δ{N_{eff}}}$. Besides, in this scenario, the new contribution to $ΔN_{\rm eff}$ is highly correlated with the dark matter sector. Thus, one can explore such feebly interacting dark matter particles (FIMP) by the precise measurement of $ΔN_{\rm eff}$ using the current (Planck2018) and forthcoming (CMB-S4 \& SPT3G) experiments.
