I am an old (41-Years-old) physics graduate. I pretty much quit to "frequent physics" 10 years ago and my ability to manage physics is a bit rusty.
I was fascinated with [Quantum Gravity](http://en.wikipedia.org/wiki/Quantum_gravity) (QG) theory and especially with the [Causal Dynamical Triangulation](http://en.wikipedia.org/wiki/Causal_dynamical_triangulation) (CDT) model developed by Loll and Ambjørn and the related approach to quantum gravity that like [Loop Quantum Gravity](http://en.wikipedia.org/wiki/Loop_quantum_gravity) (LQG) is background independent.

http://arxiv.org/abs/hep-th/0509010 

http://arxiv.org/abs/1105.5582 

I was wondering what would be the minimum mathematical/Physical background required to study this theory given that as graduate I learnt the following arguments on modern physics

 - Nuclear physics

 - Quantum Mechanics

 - Special Relativity and Electrodynamics

 - Introduction to the Structure of Matter

I know this is a quite naive question but it is never too late to learn, it says.