Pj. Dortmans et K. Amos, SPECIFICATION OF KOWALSKI-NOYES F RATIOS FOR COUPLED-CHANNELS, Physical review. C. Nuclear physics, 48(4), 1993, pp. 2112-2113
We show that by a slight redefinition, the (real) Kowalski-Noyes f rat
ios can be defined for coupled as well as uncoupled channels, and, wit
h this, we find a separable representation of t matrices whose complex
nature is dependent only on on-shell observables.