Einstein-Yang-Mills-Dirac theory

This is a theory in physics that describes gravity together with the Yang-Mills fields and coupled to fermionic matter. 

The three components are:

Einstein: Gravity and spacetime geometry. The energy and momentum of Yang-Mills fields and fermions contribute to spacetime curvature. 

Yang-Mills: Gauge interactions and internal geometry.

Dirac: Fermionic matter, obeying a curved spacetime Dirac equation. Fermions simultaneously interact with gravity and gauge fields. 

These three sectors are coupled, a particularly clean meeting point of geometry and gauge theory.