In the 1990s it was realized by Edward Witten (building on previous insights by Michael Duff, Paul Townsend, and others) that the limit of type IIA string theory in which the string coupling goes to infinity becomes a new 11-dimensional theory called M-theory [REF].
The mathematical treatment of type IIA string theory belongs to symplectic topology and algebraic geometry, particularly Gromov-Witten invariants.