  Using the approximate conformal invariance of QCD at high energies we
consider a simple AdS black disk model to describe saturation in DIS. Deep
inside saturation the structure functions have the same power law scaling, F_T
~ F_L ~ 1/x^w, where w is related to the expansion rate of the black disk with
energy. Furthermore, the ratio F_L /F_T is given by the universal value
(1+w)/(3+w), independently of the target. For virtual photon-photon scattering
at high energies we obtain explicit expressions and ratios for the total cross
sections of transverse and longitudinal photons in terms of the single
parameter w.
