arXiv 0806.49382008-06physics.class-phphysics.optics

Observation of negative impulse velocity in free space

Neil V. Budko

备注：: 4 pages, 3 figures, typo in eq.(2) corrected
发表信息：: Phys. Rev. Lett. 102, 020401 (2009)
DOI：: 10.1103/PhysRevLett.102.020401

英文摘要：

Since the 1983 definition of the speed of light in vacuum as a fundamental constant with the exact value of 299792458 m/s the question remains as to what apart from the wavefront travels at that speed. It is commonly assumed that the entire wave-packet or an impulse of the electromagnetic radiation in free space does. Here it is shown, both theoretically and experimentally, that there exists a region close to the source, where, while the wave-front travels at the speed of light, the individual impulses comprising the body of the wave-packet appear to slow down and even go backwards in time. This three-dimensional near-field late-time effect may also explain some of the free-space superluminal measurements.

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