High-energy scattering and D-pair creation in Matrix string theory

In this paper we use the Matrix string approach to begin a study of high-energy scattering processes in M-theory. In particular we exhibit an instanton-type configuration in 1 + 1 super-Yang-Mills theory that can be interpreted as a non-perturbative description of a string interaction. This solution is used to describe high-energy processes with non-zero longitudinal momentum exchange, in which an arbitrary number of eigenvalues get transferred between the two scattering states. We describe a direct correspondence between these semi-classical SYM configurations and the Gross-Mende saddle points. We also study in detail the pair production of D-particles via a one-loop calculation which in the 1 + 1-dimensional gauge theory language is described by the (perturbative) transition between states with different electric flux. Finally, we discuss a possible connection between these calculations in which D-particle production gives important corrections to the Gross-Mende process.