Which fields of mathematics use differential forms most often?

[altcmdesc]

I'm just wondering: in what field of mathematics are differential forms frequently used by professional mathematicians?

 

[olliemath]

If you mean proffessional mathematicians as in researchers then geometers.. in various areas of differential, algebraic, Riemannian, noncommutative geometry etc. or mathematical phycisists involved in general relativity and string theory, or differential topologists.. there might be other people that use them every now and then.. for example you could try doing e.g. stochastic analysis on manifolds in which case you'd probably need them