  Kinks, vortices, 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 non-homogeneous boson
condensation. I will review the related QFT formalism, the spontaneous
breakdown of symmetry framework in which the defects appear and discuss finite
temperature effects, also in connection with phase transition problematics.
