arXiv 0806.37132008-06hep-phastro-phhep-th

宇宙射线和寻找洛伦兹不变性破坏

Cosmic Rays and the Search for a Lorentz Invariance Violation

Wolfgang Bietenholz

备注：: 81 pages, 15 figures, some points extended and improved, references added
DOI：: 10.1016/j.physrep.2011.04.002

摘要：

本文介绍了在宇宙射线中寻找洛伦兹不变性破坏（LIV）信号的研究进展。我们首先概述了宇宙射线的基本方面，重点是超高能射线（UHECR）。讨论了宇宙质子的Greisen-Zatsepin-Kuz'min（GZK）能量截止，该截止是由于在宇宙微波背景（CMB）中产生的质子而引起的.在质子静止坐标系中，这是一个能量适中的过程。如果洛伦兹变换甚至在因子$γ\sim O(10^{11})$上也适用，则可以在实验室中高精度地研究它。对于较重的原子核，由于光致衰变，能量衰减甚至更快，同样如果这个过程是洛伦兹不变的。因此，洛伦兹对称性的可行性高达巨大的伽马因子-远远超出加速器测试-是一个中心问题。接下来，我们评论的概念方面的洛伦兹不变性和自发破缺的可能性。这可能会导致轻微的粒子依赖的“最大吸积速度”。讨论了它们在宇宙射线衰变、切伦科夫辐射、GZK截止和中微子振荡中的作用。我们还审查了宇宙γ射线中的LIV搜索。对于多TeV的伽马射线，我们可能会遇到另一个与CMB的透明度有关的难题，类似于GZK截止。在伽马射线暴中发射的光子能量较低，但它们非常长的路径提供了接近普朗克尺度的信息。到目前为止还没有观察到LIV。然而，即使是非常微小的LIV效应也可能彻底改变对宇宙射线物理学的预测。一个附录专门介绍皮埃尔·俄歇合作组织最近提出的假设，该假设确定了附近的活动星系核-或它们旁边的物体-可能是UHECR源。

英文摘要：

This is an introductory review about the on-going search for a signal of Lorentz Invariance Violation (LIV) in cosmic rays. We first summarise basic aspects of cosmic rays, focusing on rays of ultra high energy (UHECRs). We discuss the Greisen-Zatsepin-Kuz'min (GZK) energy cutoff for cosmic protons, which is predicted due to photopion production in the Cosmic Microwave Background (CMB). This is a process of modest energy in the proton rest frame. It can be investigated to a high precision in the laboratory, if Lorentz transformations apply even at factors $γ\sim O(10^{11})$. For heavier nuclei the energy attenuation is even faster due to photo-disintegration, again if this process is Lorentz invariant. Hence the viability of Lorentz symmetry up to tremendous gamma-factors - far beyond accelerator tests - is a central issue. Next we comment on conceptual aspects of Lorentz Invariance and the possibility of its spontaneous breaking. This could lead to slightly particle dependent ``Maximal Attainable Velocities''. We discuss their effect in decays, Cerenkov radiation, the GZK cutoff and neutrino oscillation in cosmic rays. We also review the search for LIV in cosmic gamma-rays. For multi TeV gamma-rays we possibly encounter another puzzle related to the transparency of the CMB, similar to the GZK cutoff. The photons emitted in a Gamma Ray Burst occur at lower energies, but their very long path provides access to information not far from the Planck scale. No LIV has been observed so far. However, even extremely tiny LIV effects could change the predictions for cosmic ray physics drastically. An Appendix is devoted to the recent hypothesis by the Pierre Auger Collaboration, which identifies nearby Active Galactic Nuclei - or objects next to them - as probable UHECR sources.

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