# a question from Weinberg's qft book

by bugl0ver
Tags: book, weinberg
 P: 2 can anybody tell me how to induce the quantum field theory as long as you admit the quantum mechanics and the reletivity? it seems that in Weinberg's book ,he shows that,but i can not quite understand thank you
 P: 4,008 Ok, we really cannot help you if you state your question like this. You need to be a whole lot more specific. What exactly do you want to know ? What concept are you not gettin' ? Please give some reference to a formula, approach, a "name", ... Also tell us something about your situation : are you a college student ?, undergrad ?, How's your QM and special relativity knowledge ? regards marlon ps : i urge you not to use Weinberg's book to study intro QFT. Have you considered Zee's book (QFT in a Nutshell) ? Are you doing this in college ?
 P: 2 i am a student learning theoretical physics.and i hav read some chapters of Zee's book.and i think i can follow his idea rather than Weinberg What i mean is that in many books such like Peskin's just tell us how to calculate,and it induce the qft so abruptly. So i think Wein's book will helpful.Maybe my question looks ugly and i think i get my answer myself now. but what i want to know now is that is qft just a tool in some sence? thank you
P: 4,008

## a question from Weinberg's qft book

QFT is the theoretical model to describe the interactions of many particle systems, caracterized by the fact that the total number of particles does not need to be a constant. This actually is what the "second quantisation" is all about. Particles can be created and annihilated. The biggest difference between QM and QFT is

1) in QM, the total number of particles is constant
2) In QFT, the fundamental property are the FIELDS while in QM they are the wavefunctions.

There are several quantum field theories like QED (describes the EM interaction), QCD (describes the strong force), etc etc

marlon

edit : check out this thread for further clarification
 Sci Advisor HW Helper P: 11,833 You can get QFT by simply applying canonical quantization to classical fields. There's nothing more to it. Daniel.
 P: 12 Hi, I recommend Dirac's Lectures on Quantum Mechanics. It is about 5 bucks and is well worth it. The 2nd lecture is "The Problem of Quantization".

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