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Amplification of electromagnetic fields by a rotating body
The Authors measure the amplification of electromagnetic waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body, as predicted by Zel’dovich in 1971.
There have been many practical proposals to verify Zel’dovich’s predictions in the classical regime 5, 6, 7, 8, relying, e.g., on use of a very large orbital angular momentum (OAM) ℓ= 10,000 or optically levitated particles spinning at GHz rates 7, restricting the size of the system to the nano-scale 9, 10 or on synthetic approaches 8. The practical impossibility to test Zel’dovich’s predictions, pointed out already in the original paper 1, is overcome here thanks to the heavy spatial confinement of the electromagnetic field in a LC resonator, compared to free space 15, and by making use of spin angular momentum. In summary, by operating in the sub-wavelength regime and using spin angular momentum, we have experimentally measured negative dissipation induced by a rotating metallic cylinder, indicating the amplification of EM waves originally predicted by Zel’dovich.
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