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A covariant gauge-invariant three-dimensional description of relativistic bound-states

D. R. Phillips·S. J. Wallace
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Abstract

A formalism is presented which allows covariant three-dimensional bound-state equations to be derived systematically from four-dimensional ones without the use of delta-functions. The amplitude for the interaction of a bound state described by these equations with an electromagnetic probe is constructed. This amplitude is shown to be gauge invariant if the formalism is truncated at the same coupling-constant order in both the interaction kernel of the integral equation and the electromagnetic current operator.

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D. R. Phillips, S. J. Wallace. 1997-08-15. A covariant gauge-invariant three-dimensional description of relativistic bound-states. https://doi.org/10.1007/s006010050084

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