Quantum Cylindrical Waves and Sigma Models
  We analyze cylindrical gravitational waves in vacuo with general polarization and develop a viewpoint complementary to that presented recently by Niedermaier showing that the auxiliary sigma model associated with this family of waves is not renormalizable in the standard perturbative sense. 
J. Fernando Barbero G., Guillermo A. Mena Marugan, Eduardo J. S.   Villase\~nor