Gravity seminar - Jelle Hartong Seminar

Abstract: I will discuss recent progress on the 1/c expansion of general relativity where c is the speed of light. This is an off shell and covariant approximation of general relativity that is similar to the post-Newtonian approximation. When matter is included there are different regimes of approximation depending on how one expands the matter sector in 1/c. I will show that one can use these techniques to derive an action principle for matter coupled Newtonian gravity which on shell is described by torsionless Newton-Cartan geometry.
Surprisingly it turns out that off shell the underlying gauge structure of non-relativistic gravity is not described by the Bargmann, i.e. centrally extended Galilei algebra, as was believed to be the case for many decades, but by a different algebra. I will conclude with some comments about applications of these ideas to string theory and holography.