The constraint algebra of quantum gravity in the loop representation
  We study the algebra of constraints of quantum gravity in the loop representation based on Ashtekar's new variables. We show by direct computation that the quantum commutator algebra reproduces the classical Poisson bracket one, in the limit in which regulators are removed. The calculation illustrates the use of several computational techniques for the loop representation. 
Rodolfo Gambini, Alcides Garat and Jorge Pullin