Spontaneous breaking of spacetime symmetries and the inverse Higgs effect

Understand

It has been long known that when spacetime symmetry is spontaneously broken, some of the broken generators may not give rise to independent gapless, Nambu-Goldstone excitations.

• We provide two complementary viewpoints of this phenomenon.
• On the one hand, we show that the corresponding field degrees of freedom have the same symmetry transformation properties as massive, matter fields.
• The "inverse Higgs constraints", sometimes employed to eliminate these modes from the theory, are reinterpreted as giving a field parametrization that makes these transformation properties manifest.