Diffeomorphism symmetry in quantum gravity models

Understand

We review and discuss the role of diffeomorphism symmetry in quantum gravity models.

• Such models often involve a discretization of the space-time manifold as a regularization method.
• Generically this leads to a breaking of the symmetries to approximate ones, however there are incidences in which the symmetries are exactly preserved.
• Both kind of symmetries have to be taken into account in covariant and canonical theories in order to ensure the correct continuum limit.