一个新出现的大爆炸核合成差异可能暗示着什么？
What could an emerging Big Bang Nucleosynthesis discrepancy be hinting at?
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中文总结 AI 辅助
研究原始氘丰度测量与标准大爆炸核合成预测的偏差，通过PRIMAT计算轻元素丰度并比较多种模型，发现vEDE成分可解决偏差，暗示宇宙学中可能存在另一个轻标量场。
中文摘要 AI 辅助
当使用从符合宇宙微波背景（CMB）数据的ΛCDM模型推断出的重子密度时，原始氘丰度的最新测量值与标准大爆炸核合成（BBN）的几个最先进预测存在约2σ的偏差。对于试图解决哈勃张力的模型，如早期暗能量（EDE），这种偏差增加到约3σ，EDE通常预测比ΛCDM更大的重子密度。我们测试这种差异是否可能指向BBN期间的非标准膨胀历史。我们用PRIMAT计算轻元素丰度，并比较ΛCDM、一个ΔNeff扩展和一个极早期暗能量（vEDE）成分。对于vEDE，我们对ΔH/H进行采样，即氘燃烧冻结和氦-4聚变基本结束时膨胀率的分数增加。在EDE宇宙学中使用BBN加上CMB重子密度约束的贝叶斯分析给出，在氘燃烧时期，即温度TD≃0.03MeV时，ΔH/H = 0.087+0.036−0.037，并且没有残余偏差。vEDE成分在较大的CMB重子密度下保持观测到的氘丰度，同时仅对氦-4有轻微影响。相比之下，额外辐射过于有效地提高了氦-4丰度，并且无法使重子密度测定结果一致。与暴胀、暗能量和EDE一起，我们的结果暗示宇宙学中存在另一个轻标量场。
英文摘要
The latest measurement of the primordial deuterium abundance is in $\sim 2σ$ tension with several state-of-the-art predictions of standard Big Bang nucleosynthesis (BBN), when using the baryon density inferred from the $Λ$CDM model fit to cosmic microwave background (CMB) data. This tension increases to $\sim 3σ$ for models attempting to solve the Hubble tension, such as early dark energy (EDE), which generally predict a larger baryon density than in $Λ$CDM. We test whether this discrepancy could be pointing to a non-standard expansion history during BBN. We compute light-element abundances with PRIMAT and compare $Λ$CDM, a $ΔN_{\rm eff}$ extension, and a very early dark energy (vEDE) component. For vEDE, we sample $ΔH/H$, the fractional increase of the expansion rate while deuterium burning is freezing out and helium-4 fusion is mostly over. The Bayesian analysis using BBN plus the CMB baryon-density constraint in the EDE cosmology gives $ΔH/H = 0.087^{+0.036}_{-0.037}$ during the deuterium burning epoch, i.e. at a temperature $T_{\rm D}\simeq0.03\,{\rm MeV}$, and no residual tension. The vEDE component preserves the observed deuterium abundance at the larger CMB baryon density while only mildly affecting helium-4. By contrast, extra radiation raises the helium-4 abundance too efficiently and does not reconcile the baryon density determinations. Together with inflation, dark energy, and EDE, our results hint at the presence of another light scalar field in cosmology.
