ABSTRACT
Topological defects are an almost generic phenomena ill nature and have already been detectcd in a number of laboratory contexts where symmetry breaking phase transitions take place (for examplc, superconductors, superfluids or nematic liquid crystals). Probably the most exciting possibility, however, is that they may be formed during spontaneous symmetry breaking at a phase transition in the early universe. Since most symmetry breaking schemes appear to allow their existence, it seems sensible to consider their cosmological implications. A vast literature exists on this subject (see, for example, recent reviews [1, 2]). Here, we consider specifically the roles that they may play in cosmic structure formation.
