I was just reading Forbes' list of the world's most influential thinkers, and the profile on Ed Witten mentioned how research on string theory lead to entirely new mathematics. My question is, how has string theory impacted mathematics? How much original mathematics has it lead to? Do non-string theorists use this math? P.S. I know almost nothing about string theory, so even though I know there are different types of string theory, I'm lumping them together here.