标题： 超高能宇宙射线：理论挑战 显示英文标题

标题： Ultra High Energy Cosmic Rays: The theoretical challenge

摘要： 超高能宇宙射线的起源仍然是一个谜。 宇宙射线谱中缺乏高能截止以及到达方向的各向同性分布，强烈限制了大多数为这些粒子产生而提出的模型。 综述了目前关于理论建议的现状。 天体物理加速器以及自上而下的情景及其最一般的特征一起被回顾。 这些超高能粒子的起源和性质将通过未来的观测进行检验，并可能表明并限制粒子物理学标准模型之外的物理。 显示英文摘要

摘要： The origin of the highest-energy cosmic rays remains a mystery. The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions have strongly constrained most models proposed for the generation of these particles. An overview of the present state of theoretical proposals is presented. Astrophysical accelerators as well as top-down scenarios are reviewed along with their most general signatures. The origin and nature of these ultra-high energy particles will be tested by future observations and may indicate as well as constrain physics beyond the standard model of particle physics.