I'm currently learning about the renormalization group (RG) in condensed matter physics and just want to clarify a couple of things:
When doing the RG transformation, there's a flow to a fixed point. A coupling constant is a relevant operator (or relevant coupling, depending on which book you look at) if it gets larger as the transformation continues, and flows towards the fixed point.
Have I understood that correctly?
If doing perturbative renormalization, is it right that if you have a relevant operator it is not possible to use that operator in a perturbative expansion because it's large once the transformations are done (even if it was small to start with - before the RG transformations were done)?