Changes in the meson-nucleon coupling constant and the vertex form factor in nuclear matter are studied in a modified Skyrme Lagrangian including the sigma-meson field that satisfies the scale invariance. Renormalization of the axial-vector coupling constant, and the nucleon mass are studied in a consistent model. The results are consistent with the empirical evidence. A calculation of pi N commutator, sigma-term, indicates that the medium changes its magnitude considerably.
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