Algebraic prediction of resonance couplings from assumptions about zero trajectory slopes

The slopes of the amplitude zeros in the Mandelstam plane passing through the intersection of s-channel I = 3/2 resonances with the u-channel nucleon pole are considered for pion-nucleon scattering, pion production by vector-and axial-vector currents and for Comptom scattering. New striking regularities relevant for the construction of explicit dual models involving fermions and currents are found: If one demands the zero slopes to be equal for all helicity amplitudes of the same process, the spin- and parity structure of the resonance excitation is predicted in good agreement with experiment. Demanding the zeros to pass the intersection points close to the direction t approximately const., the right order of magnitude of the resonance couplings is obtained. (orig.)