发表机构
International Centre for Theoretical Sciences（国际理论科学中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究探讨引力坍缩对小尺度发电机放大磁场的影响，发现坍缩可显著加速发电机，使磁场在坍缩时间内达到动力学显著强度，影响第一代恒星与星系的形成与演化。
AI 中文摘要
在此，我们探讨了在第一代恒星与星系形成过程中，小尺度发电机（SSD）对磁场的放大作用。引力坍缩持续改变湍流速度和长度尺度，这使得小尺度发电机与在稳态湍流中运行的发电机有本质不同。在arXiv:2503.19131中，我们发展了湍流发电机的超共动（supercomoving）表述，并表明坍缩过程中发电机增长率的增加导致在运动学阶段磁场呈超指数（SE）放大。在此，我们证明坍缩也加速了较慢的非线性阶段，使磁能能够达到逐渐更大的尺度。我们将此框架应用于第一代恒星和第一代星系形成，发现坍缩的影响强烈依赖于发电机效率。如果发电机足够快，磁场在显著坍缩发生前就达到饱和，几乎没有进一步加速的空间。在相反的极端情况下，如果发电机太慢，发电机放大仍然较弱，磁通冻结占主导。在这两个极限之间，坍缩可以显著加速发电机，在探索的参数空间中加速超过10倍，使得在可用的坍缩时间内能够发展出动力学上显著的磁场。非线性的逐尺度饱和进一步产生了与系统不可忽略部分相关的磁场。我们提供了最终场强和相关尺度的估计及标度关系，以及它们对暗物质晕、湍流、发电机和坍缩参数的依赖。动力学重要磁场的较早出现可以影响碎裂、角动量输运以及第一代恒星和星系的后续演化。
英文摘要
Here, we explore magnetic field amplification by the small-scale dynamo (SSD) during the formation of the first stars and galaxies. Gravitational collapse continuously modifies turbulent velocities and length scales, making the SSD fundamentally different from a dynamo operating in stationary turbulence. In arXiv:2503.19131, we developed a supercomoving formulation of turbulent dynamos and showed that the increasing dynamo growth rate during collapse leads to super-exponential (SE) magnetic field amplification in the kinematic stage. Here, we show that collapse also accelerates the slower nonlinear stage, allowing magnetic energy to reach progressively larger scales. We apply this framework to first-star and first-galaxy formation and find that the impact of collapse depends strongly on the dynamo efficiency. If the dynamo is sufficiently fast, the field reaches saturation before substantial collapse occurs, leaving little room for further acceleration. At the opposite extreme, if the dynamo is too slow, dynamo amplification remains weak and flux freezing dominates. Between these limits, collapse can substantially accelerate the dynamo, with speed-ups of >10 in the parameter space explored, enabling dynamically significant fields to develop within the available collapse time. Nonlinear scale-by-scale saturation further produces fields correlated on a non-negligible fraction of the system. We provide estimates and scaling relations for the final field strength and correlation scale and their dependence on halo, turbulence, dynamo, and collapse parameters. The earlier emergence of dynamically important fields can affect fragmentation, angular-momentum transport, and the subsequent evolution of the first stars and galaxies.
Comments27 pages, 16 figures, comments are welcome
