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nucl-th1993
Perturbation schemes for systems of nucleons and pions: The relationship of covariant perturbation theory, the convolution integral and time-ordered perturbation theory
D. R. Phillips, I. R. Afnan
This paper is the first in a series of three which attempt to resolve the difficulties that have plagued the problem for the past ten years. Various theoretical inconsiste…
nucl-th1993
A Gauge Invariant Unitary Theory for Pion Photoproduction
C. H. M. van Antwerpen, I. R. Afnan
A covariant, unitary and gauge invariant theory for pion photoproduction on a single nucleon is presented. To achieve gauge invariance at the operator level one needs to include bo…