E. Brezin, V.A. Kazakov, "Exactly solvable field theories of closed strings," Physics Letters B, 236, 144-50, 15 February 1990.
Edouard Brezin (Ecole Normale Superieure, Paris): "String theory, formulated as a random, two-dimensional surface--the world-sheet swept by the string in its motion, with a random metric tensor--was expressed as a two-dimensional version of quantum gravity. The usual approach for investigating string theories is perturbative: that is, one considers surfaces of increasing genuses (or number of handles). The calculations of higher genuses, however, require a sophisticated mathematical apparatus and are extremely tedious. A discrete [noncontinuous] investigative approach to string theory (a priori appropriate only for numerical treatment) leads to explicit analytic solutions in the continuum limit for a number of models. The solution is obtained as a differential equation in the coupling constant, which generates the whole perturbation expansion and allows one to discuss quantitatively nonperturbative issues. In this first article (and ...
