Ambjørn began in the early 1990s searching for a physics model that bonded quantum mechanics and relativistic gravity in a way that didn't require supersymmetry. By 1994, he argued a simpler way to represent quantum gravity was to use Lorentzian space-time geometry as a framework. His first major publication on the lattice model that would become CDT theory was released in 1998. It was then that he and Renate Loll made triangulation and the causal approach the cornerstones to the lattice gauge theory.
As of 2007, Ambjørn continues to research lattice gauge, string, and quantum gravity theories; matrix models and their applications; and statistical theories of random surfaces and paths. He is currently sharing a position as a professor at the Niels Bohr Institute and the Radboud University Nijmegen.
- Markopoulou, F., Smolin, L. "Gauge Fixing in Causal Dynamical Triangulations." Perimeter Institute for Theoretical Physics. 23 May 2006.
- 2004 Conference Journal