由AMR模拟校准的轴子弦网络产生的CMB双折射
CMB Birefringence from Axion String Networks Calibrated to an AMR Simulation
中文总结 AI 辅助
本文通过AMR模拟校准轴子弦网络的环交叉模型，预测CMB双折射，结合观测约束电磁异常系数，排除最小大统一理论预测，并探讨其对各向同性双折射证据的意义。
中文摘要 AI 辅助
宇宙中可能存在轴子弦的宇宙学网络。如果类轴子粒子与电磁相互作用，该网络会诱导宇宙微波背景（CMB）偏振产生空间变化的双折射，这可通过当前及下一代CMB实验探测。我们针对早期宇宙中轴子弦网络动力学的大尺度自适应网格细化（AMR）模拟，对环交叉模型进行校准，并利用该校准模型预测从复合时期到现今的CMB双折射。我们发现，CMB观测中未探测到各向异性双折射，对轴子-光子耦合$g_{a\beta\beta} = - \frac{\beta \times \text{em}}{\beta f_a}$中的电磁异常系数$\beta$施加了严格的上限。对现有各向异性双折射测量的联合分析，在95%置信水平（C.L.）下约束$|\beta| < 0.24$，该约束独立于Peccei-Quinn标度$f_a$，前提是轴子为超轻且网络存续至今。此限制严格约束了超轻轴子的高能嵌入理论，在高置信度下排除了电磁异常系数的最小大统一理论预测。此外，我们还讨论了轴子弦起源对近期报道的各向同性双折射证据的意义。
英文摘要
A cosmological network of axion strings may exist in the Universe today. If axion-like particles couple to electromagnetism, such a network induces spatially varying birefringence in the polarization of the cosmic microwave background (CMB), which can be probed by current and next-generation CMB experiments. We calibrate a loop-crossing model against a large-scale adaptive-mesh-refinement (AMR) simulation of axion-string network dynamics in the early Universe and use the calibrated model to predict CMB birefringence from recombination to today. We find that the non-detection of anisotropic birefringence in CMB observations places a strong upper bound on the electromagnetic anomaly coefficient $\mathcal{A}$ that enters the axion-photon coupling $g_{aγγ} = - \mathcal{A} α_\mathrm{em} / πf_a$. A joint analysis of available anisotropic birefringence measurements constrains $|\mathcal{A}| < 0.24$ at 95% C.L., which is independent of the Peccei-Quinn scale $f_a$, assuming that the axions are hyperlight so that the network survives until today. This limit strongly restricts the high-energy embedding of hyperlight axions, excluding the minimal Grand Unified Theory prediction for the electromagnetic anomaly coefficient at high significance. In addition, we discuss the implications of an axion-string origin for the recently reported evidence of isotropic birefringence.
