Quantum fields with topological defects
  Domain walls, strings and monopoles are extended objects, or defects, of quantum origin with topologically non--trivial properties and macroscopic behavior. They are described in Quantum Field Theory in terms of inhomogeneous condensates. We review the related formalism in the framework of the spontaneous breakdown of symmetry. 
M.Blasone, P.Jizba, G.Vitiello