(Re-)Inventing the Relativistic Wheel: Gravity, Cosets, and Spinning Objects

Understand

Space-time symmetries are a crucial ingredient of any theoretical model in physics.

• Unlike internal symmetries, which may or may not be gauged and/or spontaneously broken, space-time symmetries do not admit any ambiguity: they are gauged by gravity, and any conceivable physical system (other than the vacuum) is bound to break at least some of them.
• Motivated by this observation, we study how to couple gravity with the Goldstone fields that non-linearly realize spontaneously broken space-time symmetries.
• This can be done in complete generality by weakly gauging the Poincare symmetry group in the context of the coset construction.