CRITICAL-BEHAVIOR OF 3 INTERACTING STRINGS

The unbinding of three strings in a plane which interact via short-ran ged attractive potentials is studied using both transfer-matrix method s and Monte Carlo techniques. In the symmetric case, for which the two outer strings have the same line tension, the critical behavior depen ds on the relative flexibility of the inner string in a nonuniversal f ashion. In the asymmetric case, the strings unbind in two successive u nbinding transitions at two different temperatures. Renormalization-gr oup arguments predict that these results are also applicable to the ad hesion and unbinding of three membranes.