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Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture
For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications
Constructing the general partial waves and renormalization in EFT
We construct the general partial wave amplitude basis for the
scattering, which consists of Poincar\'e Clebsch-Gordan coefficients, with
Lorentz invariant forms given in terms of spinor-helicity variables. The inner
product of the Clebsch-Gordan coefficients is defined, which converts on-shell
phase space integration into an algebraic problem. We also develop the
technique of partial wave expansions of arbitrary amplitudes, including those
with infrared divergence. These are applied to the computation of anomalous
dimension matrix for general effective operators, where unitarity cuts for the
loop amplitudes, with an arbitrary number of external particles, are obtained
via partial wave expansion.Comment: 6 pages, 1 figure, 1 tabl
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