A particular class of focused, pulsed light beams can propagate self-similarly in free space at a fixed group velocity. Now, scientists present a law of refraction that determines how the group velocity of these beams changes as they refract at an interface between two materials.

中文翻译：

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折射时空波包

一类特定的聚焦脉冲光束可以以固定的群速度在自由空间中自相似地传播。现在，科学家提出了折射定律，该定律确定了这些光束在两种材料之间的界面处折射时，其群速度如何变化。