Effective field theories of two-dimensional lattice models of fluctuating
loops are constructed by mapping them onto random surfaces whose large scale
fluctuations are described by a Liouville field theory. This provides a
geometrical view of conformal invariance in two-dimensional critical phenomena
and a method for calculating critical properties of loop models exactly. As an
application of the method, the conformal charge and critical exponents for two
mutually excluding Hamiltonian walks on the square lattice are calculated.Comment: 4 RevTex pages, 1 eps figur