Mathematical physicists understand the theory of how to do it, but have difficulty obtaining practical results. Pure mathematicians do it rigorously. Quantum physicists can either know how fast they do it, or where they do it, but not both. Representation theorists do it for Schur. Ring theorists do it non-commutatively.
Set theorists do it with cardinals.
Set theorists do it with morass. Statisticians probably do it. Topologists do it on rubber sheets. Topologists do it openly. Togologists do it in multiply connected domains.