On-shell expansion of the effective action:Smatrix and the ambiguity-free stability criterion
R. Fukuda, M. Komachiya, M. Ukita · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1988
The expansion formula of the effective action in terms of the connected S-matrix elements is derived. They are expressed in terms of the on-shell quantities. The correct stability criterion of the given solution is discussed. It is free from any ambiguities which are the subjects of recent controversy.