Off-Shell Amplitudes in Two Dimensional String Field Theory

Abstract

In this note we present an explicit procedure for the regularization of tree level amplitudes involving discrete states, using open string field theory. We show that there is a natural correspondence between the discrete states and off--shell states, later acting as a regularized version of the former. A general off-shell state corresponds to several physical states. In order to obtain the well--defined $S$ matrix elements one has to choose representatives close but not equal to the desired values of external momenta. The procedure renders finite all $4$-point amplitudes with an even number of (naively) divergent channels even after the regularization is removed. The rest of the amplitudes can be defined by means of such regularization.