SELF-INTERSECTION NUMBERS AND RANDOM SURFACES ON THE LATTICE

String theory in four dimensions has the unique feature that a topolog ical term, the oriented self-intersection number, can be added to the usual action. It has been suggested that the corresponding theory of r andom surfaces would be free from the problem encountered in the scali ng of the string tension. Unfortunately, in the usual dynamical triang ulation it is not clear how to write such a term. We show that for ran dom surfaces on a hypercubic lattice however, the analogue of the orie nted self-intersection number I[sigma] can be defined and computed in a straightforward way. Furthermore, I[sigma] has a genuine topological meaning in the sense that it is invariant under the discrete analogue of continuous deformations. The resulting random surface model is no longer free and may lead to a non-trivial continuum limit.