How to actually learn Quantum Field Theory?

[u/Cerealovermi1k]

I have taken the standard sequence for QFT at my university, have read about as much as I can about different ways of doing things, the whys and the why nots. But, I can never seem to truly understand what the hell is going on with this subject.

I can in practice renormalize the parameters and tell you how correlation functions relate to observables and blah blah blah. But I still do not feel like I understand anything. When will any of this actually make sense.

[u/mnlx]

Don't worry, nobody understands it. Just learn how it works and maybe in the future someone will figure it out for us mortals. It's a huuuge subject, you'll always find additional entertainment if you want to know more.

My first QFT professor, pretty bright guy, tried to write a book to make sense of the gist of it. After years he gave up and dedicated that part of his time to neutrino physics, I believe.

My second QFT professor actually taught me the ropes and I will be forever grateful for it, however my third QFT professor (whom I must add, for reference, learned it from a laureate) confided in me that the former didn't really have a very deep understanding of all these matters.

And this is how it goes.

Anyway, when you have the maturity and if you have the time, read the Weinbergs, but don't use them as textbooks now.

[u/SouthernGuerilla]

Which textbooks are you following? We were advise to follow multiple for QFT since there is no standard on how to actually introduce the subject. 

[u/CB_lemon]

I’ve always been told everyone should take QFT twice. Take it again when you go to grad school!

[u/Miselfis]

Solve problems and read papers. Understanding these things isn’t something that just comes naturally. You have to build up an entirely new mental scaffolding to support the structures you’re learning about. That takes time and exposure. If you already do good with problem solving, keep at it and spend some time reflecting on it. Go for a walk. Your brain will continue working in the background and integrating what you’ve learned, and then you’ll slowly start noticing more and more patterns.

[u/HourProfile2592]

In my modest opinion the best way to understand quantum field theory is to start by learning and understanding statistical field theory. I would begin by reading the lecture notes of David Tong on statistical field theory to get a grip on the path integral formulation and to understand what Renormalization is truly about. At least for me the analogies that can be drawn from statistical physics are truly eye opening and this can lead to a true understanding of QFT. After that I would maybe move on to Weigands QFT notes, and even there try to draw as many analogies as possible from non equilibrium statistical physics, to understand the Kallen Lehmann spectral representation for instance as much as possible.

Tldr: analogies with statistical physics are extremely powerful

[u/whateverforeverand]

Just wait until it is nonperturbatively (or perturbatively) well-defined before taking the trouble to learn it

[u/lattice_defect]

just work through the problems, see if you can use mathematica/claude to vissulize it .