Transition from soft to hard Pomeron in the structure functions of hadrons at small x from holography

We study the nucleon and pion structure functions at the small Bjorken-x region in the framework of holographic QCD with a special emphasis on the roles of anti-de Sitter (AdS) space wave functions. Using the Brower-Polchinski-Strassler-Tan kernel for the Pomeron exchange and calculating its coupling to target hadrons in the AdS space, we obtain F-2 structure functions at the small x. Results for the proton F-2(p) as well as the pion F-2(pi) are consistent with experimental data of the deep inelastic scattering and the forward electroproduction of a neutron. Observed Q(2) dependence of the Pomeron intercept is well reproduced from soft nonperturbative (Q(2) similar to 0) to hard perturbative (Q(2) >> 1 GeV2) region. We find the interplay between soft and hard Pomerons is closely related with behavior of AdS wave functions of hadrons and the virtual photon.