From topological to topologically massive gravity through the gauge principle
arXiv:1905.05003 · doi:10.1140/epjp/s13360-020-00210-4
Abstract
It is well known that three-dimensional Einstein's gravity without matter is topological, i.e. it does not have local propagating degrees of freedom. The main result of this work is to show that dynamics in the gravitational sector can be induced by employing the gauge principle on the matter sector. This is described by a non-dynamical fermion model that supports a global gauge symmetry. By gauging this symmetry, a vector-spinor field is added to the original action to preserve the local gauge invariance. By integrating out this spin-3/2 field, we obtain a gravitational Chern-Simons term that gives rise to local propagating degrees of freedom in the gravitational sector. This is defined, after the gauging, by topologically massive gravity.
5 pages, this essay has received an Honorable Mention from the Gravity Research Foundation - 2019 Awards for Essays on Gravitation