D粒子背景和真空Refractive Indices中弦的时滞
Time Delays of Strings in D-particle Backgrounds and Vacuum Refractive Indices
摘要：
利用弦/D-膜散射振幅计算中的标准技术，我们评估了膜世界场景中开弦离开D-粒子的散射。D粒子被看作是围绕着三个循环的D3膜，它们嵌入膜世界构成了一个交叉膜的例子，其中弦被拉伸，代表了标准模型（SM）粒子在低能极限下的各种类型的激发。我们的分析，揭示了有趣的和新颖的选择规则所产生的因果时间延迟，成比例的入射物质状态的能量，从分裂，捕获和重新发射后者的D粒子的过程。特别是，我们发现，有相对较大的时间延迟，只有属于Cartan子代数的SM规范群，其中特别包括光子的激发。我们讨论了这些结果的时空泡沫模型预测一个非平凡的真空折射率的光子和相关的宇宙γ射线现象可能的相关性。特别是，我们证明了如何低弦尺度模型可以被证伪已经在这种情况下，通过目前的天体物理观测宇宙光子，以及如何这样的观测作为一种方式来区分从高弦尺度模型。
英文摘要：
Using standard techniques in string/D-brane scattering amplitude computations, we evaluate the scattering of open strings off D-particles in brane world scenarios. The D-particles are viewed as D3 branes wrapped up around three cycles, and their embedding in brane worlds constitutes a case of intersecting branes, among which strings are stretched, representing various types of excitations of the Standard Model (SM) particles in the low-energy limit. Our analysis, reveals interesting and novel selection rules for the resulting causal time delays, proportional to the energy of the incident matter state, from the processes of splitting, capture and re-emission of the latter by the D-particles. In particular, we show that there are relatively large time delays only for excitations that belong to the Cartan subalgebra of the SM gauge group, which notably includes photons. We discuss the possible relevance of these results to the models of space time foam predicting a non-trivial vacuum refractive index for photons and the associated cosmic γ-ray phenomenology. In particular, we demonstrate how low-string-scale models can be falsified already in this context, by current astrophysical observations of cosmic photons, and how such observations serve as a way to discriminate low- from high-string scale models.
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