Speaker: Toshifumi Noumi, Hong Kong University of Science and Technology
Abstract: Spacetime symmetry breaking often appears in condensed matter physics and cosmology. In contrast to the internal symmetry case, it is known that the number of broken global spacetime symmetries does not coincide with that of physical Nambu-Goldstone (NG) fields in general. Correspondingly, the coset construction of effective action has to be implemented with the so-called inverse Higgs constraints to compensate such a mismatch. In this talk, I revisit the effective action construction for spacetime symmetry breaking from the local symmetry point of view. Since NG fields are generated by local transformations of order parameters, such a local picture provides a correct identification of physical NG fields. I will illustrate the importance of the local picture and revisit the coset construction. I will also discuss applications to condensed matter physics and cosmology.