标题： 原初磁场与哈勃张力 显示英文标题

标题： Primordial magnetic fields and the Hubble tension

摘要： 磁场似乎存在于几乎所有天体物理环境中，包括星系、星系团和空隙。 考虑它们的起源可以追溯到早期宇宙事件（如电弱相变或暴胀）的可能性，既有观测上的动机，也有理论上的动机。 这种原初磁场（PMF）会嵌入等离子体中，并演化以贯穿辐射时代和物质时代，直至今天。 正如本章所述，在复合之前存在于原初等离子体中的PMF可以帮助缓解哈勃张力。 随机磁场会在等离子体中诱导不均匀性，将重子推向磁能密度较低的区域，从而加速复合过程。 因此，最后散射时的声学视界会更小，这是缓解哈勃张力的一个必要条件。 有趣的是，缓解张力所需的磁场强度正好与解释星系、星系团和空隙中观测到的磁场强度一致。 这些发现激发了进一步研究存在PMF情况下复合过程的详细研究以及对该假设的观测检验。 显示英文摘要

摘要： Magnetic fields appear to be present in essentially all astrophysical environments, including galaxies, clusters of galaxies and voids. There are both observational and theoretical motives for considering the possibility of their origin tracing back to the events in the very early universe, such as the electroweak phase transition or Inflation. Such a primordial magnetic field (PMF) would remain embedded in the plasma and evolve to persist through the radiation and matter eras, and to the present day. As described in this Chapter, a PMF present in the primordial plasma prior to recombination could help relieve the Hubble tension. A stochastic magnetic field would induce inhomogeneities, pushing the baryons into regions of lower magnetic energy density and speeding up the recombination process. As a consequence, the sound horizon at last scattering would be smaller, which is a necessary ingredient for relieving the Hubble tension. Intriguingly, the strength of the magnetic field required to alleviate the tension is of the right order to also explain the observed magnetic fields in galaxies, clusters of galaxies and voids. These findings motivate further detailed studies of recombination in the presence of PMFs and observational tests of this hypothesis.