So, do we have to draw a dividing line within QM, such that non-relativistic QM is on one side, and relativistic QM and QFT are on the other?
Are you deliberately being obtuse here?
Non-relativistic anything (substitute any word you like physics, QM, momentum, energy) is a simplification of whatever you are doing and is valid SO LONG AS YOU KNOW THE SPEEDS ARE LOW RELATIVE TO THE SPEED OF LIGHT.
In mathematics they call it approximation. So do you put approximation mathematics in a special section of mathematics that isn't really mathematics?
You layman sometimes approximate PI to 22/7 so do you put that in a special category of PI?
Doctors sometimes simplify disease treatments and go for broad spectrum antibiotics, is that a special category of medical treatment?
I think most intelligent people realize simplifications are used in just about every field that exists.
You come from a Geology background don't you so how do you treat theory simplifications in your field?
