Sects. II-IV are applied to the CSB potential caused by $\rho-\omega $ exchange in Sect. V. We show that the influence of the momentum dependence of the $\rho-\omega $ mixing matrix element can be included by allowing the $\rho$-nucleon coupling constant to violate charge symmetry. In particular, if the model of Ref.[@HHKM94] is used one needs CSB coupling constants that are 0.8% of the standard coupling constants to reproduce the results of a potential obtained without momentum dependence in the $\rho-\omega $ mixing matrix element and without CSB in the coupling constants. We summarize the analysis in Sect. VI.

Field Redefinitions And Off-Shell Propagators \[fr\]
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It has been known for quite some time that value of an off shell propagator is completely dependent on the choice of field. This is an example of a general theorem proved by Haag[@Haag], Ruelle[@Ruelle], and Borchers[@Borchers] which has been discussed by Coleman, Wess and Zumino[@Coleman]. The off-shell propagators depend on the choice of interpolating fields, whereas all S-matrix elements are independent of this choice. Thus an off-shell propagator, taken in isolation, can have no physical meaning.

To illustrate why this is so, let us consider the simplest possible case, the field corresponding to 