A way one counts degrees of freedom(i.e. independent entries of the metric tensor ) in General Relativity is this: one goes to the linearized version, vacuum solution, and he sees that there are two independent polarizations(e.g. L-R).
First: how can I know that the number of degrees of freedom in the linearized case are the same of the general case?
Second: I want to know in general how can I interpret physically the degrees of freedom? Or have I to see it for each system under investigation?
Third, is there other ways to count degrees of freedom? For example by Killing Vectors?