Off-diagonal generalized vector dominance in DIS and QCD

We review the generalized vector dominance (GVD) approach to DIS at small v alues of the scaling variable, x. In particular, we concentrate on a recent formulation of GVD that explicitly incorporates the configuration of the g amma* --> q(q)overbar transition and a QCD-inspired ansatz for the (q(q)ove rbar)p scattering amplitude. The destructive interference, originally intro duced in off-diagonal GVD is traced back to the generic structure of two-gl uon exchange. Asymptotically, the transverse photoabsorption cross section behaves as (In Q(2))/Q(2), implying a logarithmic violation of scaling for F-2, while the longitudinal-to-transverse ratio decreases as 1/lnQ(2). We a lso briefly comment on vector-meson production.