  We reformulate the O(N) sigma model as a loop model whose configurations are
the all-order strong coupling graphs of the original model. The loop
configurations are represented by a pointer list in the computer and a Monte
Carlo update scheme is proposed. Sample simulations are reported and the method
turns out to be similarly efficient as the reflection cluster method, but it
has greater potential for systematic generalization to other lattice field
theories. A variant action suggested by the method is also simulated and leads
to a rather extreme demonstration of the concept of universality of the scaling
or continuum limit.
