The effective theory of strings
  We show that the Nambu-Goto string, and its higher dimensional generalizations, can be quantized, in the sense of an effective theory, in any dimension of the target space. The crucial point is to consider expansions around classical string configurations. We are using tools from perturbative algebraic quantum field theory, quantum field theory on curved spacetimes, and the Batalin-Vilkovisky formalism. Our model has some similarities with the L\"uscher-Weisz string, but we allow for arbitrary classical background string configurations and keep the diffeomorphism invariance. 
Dorothea Bahns, Katarzyna Rejzner, Jochen Zahn
math-ph gr-qc hep-th math.MP