Did Albert Einstein contribute to math?

Solution 1:

Einstein gave a tremendous impetus to the development of differential geometry as a tool in doing general relativity. His contribution went far beyond introducing the index notation that currently bears his name! To cite a quick example, he deserves the credit jointly with David Hilbert for proving that the differential equations describing space-time ("the Einstein equation") is the Euler-Lagrange equation of a suitable variational functional; see Einstein-Hilbert action.