Pion form factor in improved holographic QCD backgrounds

We extend a recent numerical calculation of the pion electromagnetic form factor F-pi(Q(2)) in holographic QCD to study two important issues regarding the behavior of fields in the bulk. First, we show that using a chiral symmetry-breaking field formally satisfying the boundary conditions of the soft-wall model changes numerical results very little from the earlier calculation that ignores these constraints. Second, we use a background field that interpolates between hard-wall and soft-wall models to obtain an improved model that reproduces the desirable phenomenological features of both. In all cases, F-pi for large Q(2) is shallower than data, an effect that can be cured by relaxing the fit to one of the static observables, particularly the decay constant f(pi).