Hello, I am trying to find out (searching did not return anything useful) what kind of mathematical background one needs to understand QFT comfortably (if such state can ever be attained :D). By comfortably I mean being able to concentrate almost entirely on the physics part rather than pick up math at the same time. Specifically, I mean not only the bare prerequisites to understand the material, but also, the mathematical topics which might be a bit off the main track but prove useful nonetheless. To provide an example, after taking a first semester undergraduate quantum, I think that a solid preparation for QM would involve Linear algebra, Fourier analysis, and ODE. I am looking for similar ideas regarding QFT.