形形色色（5）
2009年10月29日, 星期四
1、Lorentz对称破坏的新限制
过去一年，寻找可能的Lorentz破坏是我研究的重点之一，Fermi GLAST观测伽玛暴的高能光子的可能延迟是最有可能发现Lorentz破坏的实验之一。曾经有人觉得Fermi可能看到了这种效应，看来是过分乐观了一点。最近有篇文章
Special relativity passes key test
指出Fermi的结果排除了在色散关系的线性层次上破坏Lorentz对称（能标已经超过Planck能标）。
摘要
The Fermi team used two relatively independent data analyses to conclude that Lorentz invariance had not been violated. One was the detection of a high-energy photon less than a second after the start of the burst, and the second was the existence of characteristic sharp peaks within the evolution of the burst rather than the smearing of its output that would be expected if there were a distribution in photon speeds. The researchers arrived at the same null result when studying the radiation from a gamma-ray burst detected in September last year, but could only reach about one-tenth of the Planck energy. Crucially, the shorter duration and much finer time structure of the more recent gamma-ray burst takes this null result to at least 1.2 times the Planck energy.