String theory in a vertex operator representation: a simple model for   testing loop quantum gravity
  The loop quantum gravity technique is applied to the free bosonic string. A Hilbert space similar to loop space in loop quantum gravity as well as representations of diffeomorphism and hamiltonian constraints on it are constructed. The string in this representation can be viewed as a set of interacting relativistic particles each carrying a certain momentum. Two different regularizations of the hamiltonian constraint are proposed. The first of them is anomaly-free and give rise to interaction very similar to that of two dimensional $\phi^4$-model. The second version of hamiltonian constraint is similar to $\phi^3$-model and contains an anomaly. A possible relation of these two models to the conventional quantization of the string based on Fock space representation is discussed. 
Artem Starodubtsev