L. Bonora et Cs. Xiong, MATRIX MODELS, TOPOLOGICAL FIELD-THEORIES AND C-LESS-THAN-OR-EQUAL-TO-1 STRING THEORY, Progress of theoretical physics. Supplement, (118), 1995, pp. 201-240
We review ordinary and extended two-matrix models and their applicatio
n to 2D gravity. After a general introduction we deal in particular wi
th two aspects: 1) the emergence from two-matrix models of n-th KdV hi
erarchies and the topological field theories associated to them; 2) th
e representation of the discrete states of the c=1 string theory by me
ans of the extended two-matrix model. These constitute two remarkable
examples of our idea that two-matrix models provide a unifying descrip
tion of 2D gravity coupled to c less than or equal to 1 conformal matt
er.