On the continuation of the dual amplitude with Mandelstam analyticity   off mass shell
  A model for the Q^2-dependent modified dual amplitude with Mandelstam analyticity (M-DAMA) is proposed. M-DAMA preserves all the attractive properties of DAMA, such as its pole structure and Regge asymptotics, and leads to a generalized dual amplitude A(s,t,Q^2). This amplitude can be checked in the known kinematical limits, i.e. it should reduce to onshell hadronic scattering amplitude for Q^2=0 and can be related to the nuclear structure function for t=0. In such a way we complete a unified "two-dimensionally dual" picture of strong interaction. By comparing the structure function F_2, resulting from M-DAMA, with phenomenological parameterizations, we fix the Q^2-dependence in M-DAMA. In all studied regions, i.e. large and low x limits as well as for the resonance region, the results of M-DAMA are in qualitative agreement with the experiment. The new feature of the M-DAMA is the possible existence, according to vector meson dominance, of Q^2 poles in negative Q^2 region, accessible in e^+ e^- annihilation. 
V.K. Magas