I'm worldbuilding a story, where a famous string theorist hires a student of mathematics to try construct a new theory. For better drama, my premise of the story is that the student never learned more than high school physics.
What kind of mathematical disciplines would be most useful for someone who has never studied relativity nor quantum mechanics to understand it as quickly as possible?
I don't know how important it is, but the basic idea is as follows. A famous physicist visits a small-town college on invitation of an acquaintance who is a professor there. While giving a talk presenting his theory, a latecoming student finds a flaw in the underlying mathematics. The theory is based on a conjecture that is unproven but assumed to be correct. The suggested counterexample gains infamy for the student - something akin to finding counterexamples for the Riemann hypothesis.
Shaken by the latest string of bad news from CERN where experimentalists fail to find supersymmetric particles predicted by his theory, he decides to invite the student to help try a new approach.
I'm not looking for hard science; I'm just looking to tell a good story with some background in math and physics, something like Leonardo making tools in Assassin's Creed.