On gravitational defects, particles and strings

Understand

We study the inclusion of point and string matter in the deSitter gauge theory, or MacDowell-Mansouri formulation of four dimensional gravity.

• We proceed by locally breaking the gauge symmetries of general relativity along worldlines and worldsheets embedded in the spacetime manifold.
• Restoring full gauge invariance introduces new dynamical fields which describe the dynamics of spinning matter coupled to gravity.
• We discuss the physical interpretation of the obtained formalism by studying the flat limit and the spinless case on arbitrary backgrounds.