The mass of the open string stretched between the brane and the anti-brane approaches a finite positive value even when the branes coincide. Similar result is obtained for a Dirichlet six brane on top of an orientifold six plane. The result for the form factors is consistent with the form factors of the sine-Gordon model found recently by Lukyanov. We discuss the origin of the structure of the free field representation for the sine-Gordon model at the critical coupling from the point of view of the lattice model. The heterotic result is compared with the associated type-I result.
Infrared finiteness is restored after resummation of divergent terms to all orders.
The resulting characteristic structure, which we call a Sudakov shoulder, represents an interesting new class of QCD predictions. Radiative corrections are taken into account exactly in the first order and within the leading logarithmic approximation in higher orders. A combined approach for accounting exact calculations and electron structure functions is used. To discuss the model-dependence of these interactions, we take the simple case of spontaneously broken supersymmetry and only two chiral superfields, associated with the goldstino and a massless matter fermion. We solve the puzzle by enlarging the non-linear realization to include a second independent invariant coupling.