Eikonal Propagators for the High-Energy Parton-Parton Scattering in Gauge Theories

By a direct resummation of perturbation theory in the limit of very high energy and small transferred momentum (the so-called "eikonal" limit), we derive expressions for the truncated-connected quark, antiquark and gluon propagators in an external gluon field, both for scalar and fermion gauge theories. These are the basic ingredients to derive "soft" high-energy parton-parton scattering amplitudes, using the LSZ reduction formulae and a functional integral approach.