# I Self education: how to proceed from QM to QFT?

1. Dec 8, 2017

### MichPod

I tried to start many books/video courses to learn QFT but this failed because of many factors, including my weak math/physics background, laziness, lack of time, lack of persistence, just to count some. The whole blame is on me, no doubt.

Still, if I was able to learn QM to some extent comparable to 50-70% B.S. (only around 40 yo., before that the same reasons worked for QM studying as well), there must be some way to proceed further.

Can somebody recommend (from their experience) some way to go into the domain of QFT? May be some set of books from easier to not-so-easy that worked for you, may be some particular video courses that worked in some similar situation?

Last edited: Dec 8, 2017
2. Dec 8, 2017

### A. Neumaier

Given your first sentence you should first improve your math/physics background. You need to understand QM well, get some knowledge of classical field theory and electrodynamics, and the basics of statistical mechanics, including second quantization. Lacking any of these you'll not understand much of the essence of QFT.

3. Dec 8, 2017

### MichPod

Which parts of statistical mechanics, btw, are related?
And is second quantization related somehow to statistical mechanics?

I do realize QFT needs much more preparation than QM and I am trying, but still looking for some shortcut...

4. Dec 8, 2017

### A. Neumaier

Yes; it is the way quantum statistical mechanics is done in practice for all but the simplest problems. A good account is the book by Linda Reichl on statistical physics. From statistical mechanics you need the second quantization formalism and the ideas surrounding critical points and the renormalization group.
The best shortcut is solidifying the basics. To swim across the English channel you better first train your swimming skills in a number of smaller lakes!

5. Dec 8, 2017

### MichPod

Is it somehow different from the second quantization as it is presented in the basic QM courses?

I would rather prefer to swim a quarter of the way, then may be get additional training as I made at least some way into the field. Of course, I am trying to get some training here and there, I am in much better shape than 2 years ago, still it is very little comparing to what is required.

6. Dec 8, 2017

### A. Neumaier

Formally it is the same, but you can see it best at work in the statistical mechanics context. And this experience counts....

Well, it is you who has to do the swimming, according to your own judgment. But your swimming experience - aka your reading and understanding of QFT - will be quite different depending on how you are prepared.

7. Dec 8, 2017

### MichPod

Well, I do recognize the necessity of learning most of the topics you mentioned (though the mention of statistical mechanics is new for me). Still, we may have very different perspectives, as my situation is very non standard for regular science people and people who educate young students.

I could probably be able to master these topics + QFT to some extent if I had classes, doing it myself in the free time is a very different story.

That is why I am interested in some "adapted" books or videos which did work for somebody.

For instance, I could recommend David Miller's QMSE courses for anybody who have troubles entering the QM - which worked for me after many other things have failed. I am looking for something of this sort for QFT.

Last edited: Dec 8, 2017
8. Dec 8, 2017

### George Jones

Staff Emeritus
Have you tried "Quantum Field Theory for the Gifted Amateur" by Lancaster and Blundell"?

9. Dec 8, 2017

### MichPod

Yes, thank you. And I am still trying... Would prefer something even more simple and elaborate, though I still have some hopes about me and this book.

10. Dec 9, 2017

### DrDu

Personally, I would try to master first non-relativistic QFT as is used to describe solid state systems. While relativistic QFT is little more than some rules to treat terms of a divergent perturbation series, in a non-relativistic context, you can always - at least in principle - write down the full hamiltonian and ground state wavefunction of the system. Many effects which are hard to understand in a relativistic context, like e.g. anomalies, have a relatively trivial analog in non-relativistic theory. There are some books which treat both non-relativistic and relativistic QFT on the same track.

11. Dec 9, 2017

### atyy

Condensed matter physics is mostly based on non-relativistic QM. In the case of many identical particles, non-relativistic QM can be re-written using the language of second quantization as non-relativistic QFT. So if you know non-relativistic QM, in principle you already know the content of non-relativistic QFT, just not the formalism.

https://www.amazon.com/Guide-Feynman-Diagrams-Many-Body-Problem/dp/0486670473 - has a chapter about second quantization

http://www.mit.edu/~levitov/8514/#lecturenotes - second quantization notes for a condensed matter course (postscript works, but not pdf)

https://www.colorado.edu/physics/phys7450/phys7450_sp10/notes/2nd_quantization.pdf - second quantization notes for a condensed matter course

http://eduardo.physics.illinois.edu/phys582/physics582.html - includes notes about non-relativistic QFT, see especially http://eduardo.physics.illinois.edu/phys582/582-chapter6.pdf

https://www.amazon.com/Quantum-Field-Theory-Gifted-Amateur/dp/019969933X - I haven't read this, but many here have recommended it, and it looks like it could be good

Last edited: Dec 9, 2017
12. Dec 9, 2017

### Staff: Mentor

Then try - QFT Demystified:
https://www.amazon.com/Quantum-Field-Theory-Demystified-McMahon/dp/0071543821

I would read both the Gifted Amateur book (I have it as well) and the following:
https://www.amazon.com/Student-Friendly-Quantum-Field-Theory/dp/0984513957

Persevere - first do the Demystified book then the other 2 in any order, then do it again.

I would also recommend as a build up the following, which I also have:
http://physicsfromsymmetry.com/

Some say, correctly IMHO, it's a bit superficial - but that has pro's and con's. When starting out being superficial can help in understanding by not getting bogged down in deeper material.

Thanks
Bill

13. Dec 10, 2017

### MichPod

Looks good for me. I'll try to go on this.

Thanks to everybody for the recomendations. I still need to digest if I need statistical physics and nonrelativistic QFT in the current time.

14. Dec 12, 2017

### Bob108

15. Dec 12, 2017

### SKHanson57

Try reading a book or books title “A Short Intriloduction To —————— series by many different authors with many different specialties? Whatever your interest are. Like a short introduction to Quantum Mechanics it’ll give you a lot of the dirt in terms that are understandable along with mathematical explanations etc.

16. Dec 12, 2017

### MichPod

Tried many times. Probably, not a style I can like and digest.

I tried. Most of the books and articles are above my level and I cannot catch up.
What I really need is THE book or THE video course which will either match my level (i.e. more detailed and more adapted at least in the first 100 pages than most of the book for QFT beginners) or will be able to bring me up to the necessary level.

I already got a recommendation to start from "QFT Demystified" which has, BTW quite a low rate at Amazon, and it was actually very inspiring and interesting for me to read its first 50 pages. And it showed me very clearly that I really really miss some basic stuff like being fluent with variations and some stuff about classical fields theory.

So, I probably need no QFT books for beginners, but rather some short and pragmatic introduction to classical fields (which QFT introductory books alone could not provide for me). Hopefully, realizing that will help me to make some more progress. I did not realize how much I am stuck because of this exactly. And I am quite optimistic now.

17. Dec 12, 2017

### A. Neumaier

I'd recommend the theoretical physics book by Honerkamp & Roemer,
https://d-nb.info/931115612/04

18. Dec 12, 2017

### MichPod

Thank you. This is not a problem for me meanwhile to find a course in classic fields theory (in addition to reading QFT Demystified which looks a very good match for me meanwhile).
As for Honerkamp & Roemer I could not find Lagrangian formalism for fields in it, nor tensor formalism QFT uses.
May be a good book, but it'll take me years to read it.
I, again, am looking for some shortcuts, wherever possible.

19. Dec 12, 2017

### MichPod

Hmm... I did not realize in the beginning that you are talking about some real book series. Well, actually, I could not find any in this series which is related to QFT.

20. Dec 13, 2017

### Thuring

Try the Susskind lectures on youtube. Some of them involve an introduction to QFT. Lot's of other good stuff too for intermediate levels. Just have to put up with occasional bad audio-visual.