Domain defects in systems of two real scalar fields

In this work we investigate the role of the symmetry of the Lagrangian on t he existence of defects in systems of coupled scalar fields. We focus atten tion mainly on solutions where defects may nest defects. When space is non- compact we find topological BPS and non-BPS solutions that present internal structure. When space is compact the solutions are nontopological sphalero ns, which may be nested inside the topological defects. We address the ques tion of classical stability of these topological and nontopological solutio ns and investigate how the thermal corrections may modify the classical sce nario.