  We revisit the problem of dipole-dipole scattering via exchanges of soft
Pomerons in the context of holographic QCD. We show that a single closed string
exchange contribution to the eikonalized dipole-dipole scattering amplitude
yields a Regge behavior of the elastic amplitude; the corresponding slope and
intercept are different from previous results obtained by a variational
analysis of semi-classical surfaces. We provide a physical interpretation of
the semi-classical worldsheets driving the Regge behavior for (-t)>0 in terms
of worldsheet instantons. The latter describe the Schwinger mechanism for
string pair creation by an electric field, where the longitudinal electric
field E_L=\sigma_T tanh(\chi/2) at the origin of this non-perturbative
mechanism is induced by the relative rapidity {\chi} of the scattering dipoles.
Our analysis naturally explains the diffusion in the impact parameter space
encoded in the Pomeron exchange; in our picture, it is due to the Unruh
temperature of accelerated strings under the electric field. We also argue for
the existence of a "micro-fireball" in the middle of the transverse space due
to the soft Pomeron exchange, which may be at the origin of the thermal
character of multiparticle production in ep/pp collisions. After summing over
uncorrelated multi-Pomeron exchanges, we find that the total dipole-dipole
cross section obeys the Froissart unitarity bound.
