物性セミナー/2006-10-6

These lectures will review symmetry-breaking phase transitions in the special case of the breaking of combined symmetries and the subsequent formation of different states with different ordering. The two most interesting systems with these futures are the Universe and superfluid $^3$He.In both cases the energy potential below the transition temperature has a complicated multidimensional profile with many local minima and saddle points, which correspond to differentstates. Consequently, not only topological defects, but also islands of differentmetastable states can be created. Using $^3$He we can analyze the properties and experimental consequences of such transitions and, in particular, the first order phase transition between the two low symmetry states.　