Primordial electromagnetic fields can strongly affect the cosmic evolution of axions, and vice versa. We show that if helical electromagnetic fields are coherently produced in the early universe, their remnants source a field velocity to the coupled axions and enhance the relic abundance of axion dark matter. We discuss the implications for the QCD axion and axion-like particles that are coupled to the SM or hidden gauge groups. For a QCD axion coupled to hidden photons, we find that the conventional window for the axion decay constant 10⁸ GeV≲ f ≲ 10¹² GeV can be completely closed due to overproduction of axion dark matter by helical electromagnetic fields as little as α Δ N_eff≳ 10^-12, where α is the gauge coupling and Δ N_eff is the effective extra relativistic degrees of freedom of the hidden photons.

原始电磁场可以强烈影响轴子的宇宙演化，反之亦然。我们表明，如果在早期宇宙中连续产生螺旋电磁场，它们的残余物会为耦合的轴子提供场速度并增强轴子暗物质的遗迹丰度。我们讨论了耦合到 SM 或隐藏规范组的 QCD 轴子和类轴子粒子的含义。对于耦合到隐藏光子的 QCD 轴子，我们发现轴子衰减常数 10 ⁸ GeV≲ f ≲ 10 ¹² GeV 的常规窗口可以完全关闭，因为螺旋电磁场产生的轴子暗物质低至 α Δ N效率_≳ 10 ^-12，其中 α 是规范耦合，Δ N_eff 是隐藏光子的有效额外相对论自由度。