Ultra-high-energy cosmic rays from topological defects

能量超过10^19 eV的最高能量宇宙射线的来源是一个谜。很难想象传统的加速机制（如活动星系核）如何达到这些能量。此外，如此高能量的质子几乎不受磁场的影响，因此它们的到达方向指向它们的来源，但在这些方向上没有看到公认的来源。这一困惑激发了对非传统来源的研究。拓扑缺陷，如畴壁、弦和单极子，可能是由早期宇宙中的相变产生的。宇宙弦也可能来自超弦理论。由于这些天体自然具有非常高的能量标度，它们有可能释放出非常大质量的粒子，这些粒子衰变产生观测到的宇宙射线。一些拓扑缺陷也可能移动得非常快，并产生非常强的磁场，从而充当加速度源。该项目将通过分析和计算机模拟计算来自各种拓扑缺陷源的预期宇宙射线通量，以便与现有观测数据和新实验的结果，特别是目前在阿根廷运行的俄歇观测站的结果进行比较。这项工作最令人兴奋的可能结果将是根据特定的源模型解释观察到的事件。但是，即使是一个否定的结果也会导致拓扑缺陷模型的重要界限。无论哪种情况，我们都将了解到关于早期宇宙学和最高能量尺度下的基础物理学的重要信息

The source of the highest energy cosmic rays, with energies above 10^19 eV, is an enigma. It is hard to see how conventional acceleration mechanisms (such as active galactic nuclei) can reach these energies. Furthermore, protons of such high energies are little affected by magnetic fields, and thus their arrival directions point back to their sources, but no generally agreed-upon sources are seen in those directions. This puzzle motivates the study of nontraditional sources. Topological defects, such as domain walls, strings, and monopoles, may have been produced by phase transitions in the early universe. Cosmic strings may also arise from superstring theory. Because such objects naturally have a very high energy scale, it is possible for them to release very massive particles which decay to produce the observed cosmic rays. It is also possible for some topological defects to move very rapidly and to produce very strong magnetic fields, and thus to act as acceleration sources. This project will calculate, by analysis and computer simulation, the expected cosmic ray fluxes from the various topological defect sources, for comparison with existing observational data and the results of new experiments, in particular the Auger observatory, now in operation in Argentina. The most exciting possible outcome of this work would be an explanation of observed events in terms of a specific source model. But even a negative result would lead to important bounds on topological defect models. In either case, we would learn important information about early-universe cosmology and fundamental physics at the highest energy scales