标题： CMB B 模极化对各向异性宇宙双折射的限制 显示英文标题

标题： Constraints on Anisotropic Cosmic Birefringence from CMB B-mode Polarization

摘要： 宇宙双折射——光在穿越宇宙时偏振平面的旋转——为观测超越标准模型的宇称不守恒物理提供了一个直接的窗口。 在本研究中，我们重新审视了宇宙双折射的各向异性成分，它导致了宇宙微波背景辐射 (CMB) 中 $B$ 模式偏振的产生。 我们采用超越薄末散射表面近似的精确理论处理方法，结合来自 SPTpol、ACT、POLARBEAR 和 BICEP 的偏振数据，对各向异性双折射的振幅进行了约束。 联合分析得出的最佳拟合振幅为 $A_{\rm CB} = 0.42^{+0.40}_{-0.34} \times 10^{-4}$，与 $2\sigma$ 范围内的零值一致，并且我们设定了 95% 置信水平的上限 $A_{\rm CB} < 1 \times 10^{-4}$。 该约束不受任何单个实验的支配，并且在包含可能的各向同性旋转角的情况下仍然稳健。 这些结果为 CMB $B$ 模偏振引起的各向异性宇宙双折射提供了重要的约束条件，并展示了即将进行的实验在提高对早期宇宙宇称破坏效应灵敏度方面的潜力。 显示英文摘要

摘要： Cosmic birefringence$-$the rotation of the polarization plane of light as it traverses the universe$-$offers a direct observational window into parity-violating physics beyond the Standard Model. In this work, we revisit the anisotropic component of cosmic birefringence, which leads to the generation of $B$-mode polarization in the cosmic microwave background (CMB). Using an exact theoretical treatment beyond the thin last-scattering surface approximation, we constrain the amplitude of anisotropic birefringence with combined polarization data from SPTpol, ACT, POLARBEAR, and BICEP. The joint analysis yields a best-fit amplitude of $A_{\rm CB} = 0.42^{+0.40}_{-0.34} \times 10^{-4}$, consistent with zero within $2\sigma$, and we place a 95\% confidence-level upper bound of $A_{\rm CB} < 1 \times 10^{-4}$. The constraint is not dominated by any single experiment and remains robust under the inclusion of a possible isotropic rotation angle. These results provide leading constraints on anisotropic cosmic birefringence from CMB $B$-mode polarization and illustrate the potential of upcoming experiments to improve sensitivity to parity-violating effects in the early universe.