Speaker
Description
Domain wall is one of the topological defects that can be created during phase transitions. The minimal and most well-studied domain wall is from $Z_2$ symmetry breaking. In this talk, we will go beyond this minimal case in two ways: embedding the $Z_2$ symmetry into a $U(1)$ and generalising the abelian discrete symmetry to non-abelian ones. On the one hand, the $Z_2$ symmetry can result from a $U(1)$ symmetry at a higher scale. In such a breaking chain, the domain walls from $Z_2$ symmetry breaking form hybrid defects with the cosmic strings from $U(1)$ symmetry breaking. On the other hand, the breaking of non-abelian discrete symmetries also generates domain walls. Adopting $S_4$ as an example, we will see these non-abelian domain walls have a richer structure and thus can lead to many interesting phenomena.
