We explore the consequences of the breaking of diffeomorphism (Diff) invariance in the electromagnetic sector. We consider the breaking of Diff symmetry down to the subgroup of transverse diffeomorphisms (TDiff) and analyze its impact on the generation and evolution of cosmic magnetic fields. We show that Diff breaking induces a breaking of conformal invariance that modifies the way in which magnetic fields evolve on super-Hubble scales. The effects of the highly conductive plasma in the evolution are also analyzed. We obtain the magnetic power spectrum today and discuss the parameter regions that yield intergalactic magnetic fields compatible with current observations.

中文翻译：

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横向微分同胚下的宇宙磁场不变


我们探讨电磁领域中微分同胚 (Diff) 不变性被打破的后果。我们将 Diff 对称性破缺考虑为横向微分同胚 (TDiff) 子群，并分析其对宇宙磁场的产生和演化的影响。我们证明，Diff 破坏会导致共形不变性的破坏，从而改变磁场在超哈勃尺度上演化的方式。还分析了高导电等离子体在演化过程中的影响。我们今天获得了磁功率谱，并讨论了产生与当前观测结果兼容的星系间磁场的参数区域。