3 common elements.

Generally these are the things you always find in teoretical physcis.
1.) Representation : The process by which we model a physical situation mathematically is called Representation

2.) Realization : The proceaa in which we find a physical situation for a mathematical model is known as Realization.

3.) Covariance : If there are one or more mathematical model i.e many mathematical equivalent representations of a physical situation, covariance is the changes in the rulesa and mathematical structures as one goes from one equivalent representation to another.