THE PERTURBATIVE APPROACH TO THE CRITICAL-BEHAVIOR OF 2-MATRIX MODELSIN THE LIMIT N-]INFINITY

We construct representations of the Heisenberg algebra by pushing the perturbation expansion to high orders. If the multiplication operators B-1,B-2 tend to differential operators of order l(2,1), respectively, the singularity is characterized by (l(1),l(2)). Let l(1) greater tha n or equal to l(2). Then the two cases, (A) ''l(2) does not divide l(1 )'' and (B) ''l(2) divides l(1)'', need a different treatment. The uni versality classes are labelled [p, q] where [p, q]=[l(1),l(2)] in case (A) and [p, q]=[l(1) + 1,l(2)] in case (B).