Deep inelastic scattering from gauge string duality in the soft wall model

Deep inelastic structure functions have been calculated by Polchinski and Strassler in gauge/string duality introducing a hard infrared (IR) cut off in AdS space. Here we investigate this problem using a soft IR cut off that leads to linear Regge trajectories for mesons. We calculate the structure functions for scalar particles in the large x regime where supergravity approximation holds and the small x regime where massive string states contribute. We also propose a hybrid model to calculate structure functions for fermions in the supergravity approximation. In the deep inelastic limit our results are in agreement with those obtained using a hard cut off.
Comment: V3: Results unchanged. We clarified the differences between the soft and hard wall models regarding the calculation of structure functions in DIS. We included a calculation of elastic form factors. We explained in more detail the hybrid model proposed for fermions. Version accepted for publication in JHEP. 20 pages, 1 Latex figure