What is Qft: Definition and 978 Discussions

In particle physics, the history of quantum field theory starts with its creation by Paul Dirac, when he attempted to quantize the electromagnetic field in the late 1920s. Major advances in the theory were made in the 1940s and 1950s, and led to the introduction of renormalized quantum electrodynamics (QED). QED was so successful and accurately predictive that efforts were made to apply the same basic concepts for the other forces of nature. By the late 1970s, these efforts successfully utilized gauge theory in the strong nuclear force and weak nuclear force, producing the modern standard model of particle physics.
Efforts to describe gravity using the same techniques have, to date, failed. The study of quantum field theory is still flourishing, as are applications of its methods to many physical problems. It remains one of the most vital areas of theoretical physics today, providing a common language to several different branches of physics.

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  1. R

    How much is this renormalization business a problem in QFT?

    How much is this renormalization business a problem in QFT? Always read it’s complete ‘hand-waving’ and arbitrary, but also that QFT is the most precise theory ever. Also found this quote: "[Renormalization is] just a stop-gap procedure. There must be some fundamental change in our ideas...
  2. H

    Exploring the Objects of Quantum Field Theory: A Brief Overview

    For some reason, I skimmed the wikipedia article on QFT, and I feel like I kind of have an idea what the basic objects are... it would be nice if I can be told if I'm way off base, or something close, or whatever. I'm trying to figure out just what the objects are first, and I'll worry about...
  3. L

    Looking for a QFT Exercise Buddy: A Grad Student's Quest for Mastery

    I'm a grad student. I've done 2 semester of QFT using Peskin but I've didn't too well due to many reasons. I now want to go back and catch up on things I should have learned better, and then learn even more - I want to be a good field theorist. I'd like to see if there's anyone in a similar...
  4. S

    A good short intro to Perturbative QFT

    Here is a paper on the arxiv, preprint of an encyclopedia entry, which might be useful to many to introduce the ideas and techniques used in perturbative quantization of different fields. If you are content to accept for the moment brief definitions instead of leisurely motivations of the...
  5. S

    Where Can I Continue Learning QFT on My Own?

    I just finished an introduction to quantum mechanics class, and I was wondering where I could learn QFT on my own (including any more QM I might need to learn before I could start QFT). I have Griffiths book, and in class we covered the first 7 chapters (which includes all the basics...
  6. W

    EPR Experiment and QFT: Are They in Conflict?

    Hi, I have a question: The EPR experiment told us the world is nonlocal. And as we know, the QFT is a local theory, there is a principle that measurement do not affect each other between spacelike points. Do the two conflict? And can we say "we can not find an experiment for now which does not...
  7. C

    QFT anomaly in electromagnetic, neutral Pion decays

    The electromagnetic neutral pion decay is a three-point interaction: it decays into two virtual and charged Kaons or Protons, of which one then radiates a photon and then annihalates with the other to produce a second photon. (Obviously, a neutral particle cannot radiate photons directly)...
  8. S

    Understanding QFT: 3 Common Questions Answered by Experts

    I have three questions about QFT. I know you can answer this questions, sure you can. - How does a standing wave look like in 3 dimensions (x,y,z). I mean an electro magnetic oscillation between two walls or in free space. I can't really imagine that thing and looked for pictures (google) but...
  9. M

    Is QFT with curved spacetime the key to quantum gravity?

    I was wondering, is there a possibillity that QFT with curved spacetime is a the path to unification? Also, what advances are there in constructing QFTs with dynamic spacetime? If this way is feasible, who are the people spearheading it?
  10. P

    Solving Problem 10.3 from Peskin's QFT Book

    Hi, I'm stuck with problem 10.3 from Peskin's QFT book. I'm trying to evaluate the 2-loop sunset diagram in massless phi^4 theory however I keep running into trouble. I'm trying to use standard feynman parameter + dimensional regularisation techniques however i keep getting stuck when it...
  11. B

    QFT thought experiment in 1+1 dimensions

    First off let me start by stating that I am aware that you must get a great amount of "snake-oil theories" on this board and that I have no interests in "peddling". I am merely a high-school student, very interested in physics, who was lucky enough to stumble across these forums. I had an idea...
  12. L

    Asking for answers to exercises of peskin's QFT?

    thanks for advices.
  13. B

    Can someone recommend books about QFT?

    I want to read papers about the QCD and superstrings, which books are better to read firstly as an introduction.
  14. A

    Peskin's QFT Book: Solutions to Problems

    Hi, I'm trying to work out the problems on peskin's book. Does anyone know that where I can find the solutions to them? It is really hard to do it all by myself. Thanks!
  15. R

    QFT Books: Best Book for Beginners

    Hello, First I want to apologize for this FAQ-like question, but I couldn't find the answer anywhere here. so...I'm looking for a good book on quantum field theory and I'm new to this subject. I've had a introductory course on quantum mechanics. I found the following on the internet: -...
  16. M

    Solving for the space-time metric in the QFT integrals

    I just heard that the cosmological constant is a coupling constant in some perturbative expansion of some QFT and can be interpreted as a mass? Is this true? Wouldn't that be interesting? That would mean that the GR effect of expansion may be responsible (or may be an equivalent expression for)...
  17. Norman

    QFT proof from Peskin and Schroeder

    I am unsure if this is the proper forum for this, since it is not actually homework... but here goes anyway. I am trying to Prove Peskin and Schroeder equation 2.33( the second equal sign) P=-\int d^3 x \pi (x) \nabla \phi (x) = \int \frac{d^3 x}{(2 \pi)^3} p a^{\dagger}_p a_p so...
  18. N

    Strings and non-commutative qft

    I've sometimes heard that there are string theory results that are quite similar to some of non-commutative qft. What are these?
  19. marlon

    Understanding Polyakov-Loop & Ward-Identity in QFT

    Can anyone give me an explanation in layman-terms of the concept of a Polyakov-loop in QFT? What does it mean fysically. I know that this is often used in lattice QCD, but why ? I have the same questions for a socalled Ward-identity regards marlon
  20. V

    QFT Textbook Recommendations and Discussion

    Hello all, I'm reading through this book now and I'd like to know if there are other people who are also doing so, have read it or are planning to read it in order to have a discussion about it. In fact, I've read before about the first half (a bit more) of Peskin and Schroeder and I think...
  21. Antonio Lao

    What is a Path in QM and QFT ?

    What is a Path in QM and QFT ? In classical mechanics, we are allowed to talk about path of a particle. But in quantum mechanics, the concept of path of a particle cannot be defined. This is due to the uncertainty principle. But Feynman talked about path integral in quantum mechanics. This...
  22. Norman

    Peskin & Schroeder: Is it a Good First Time QFT Book?

    Hello all, Just wondering if Peskin and Schroeder is a good first time QFT book? If so, what would be a good book to supplement it with? Cheers, Norm
  23. A

    QFT: Questions About Vector Field, Polarization Vectors & Space

    Hello everyone, I am now learning QFT, this theory is really abstract and daunting. I can't understand the concept of vector field. What is vector field at last? why there are four polarization vectors? I feel that the whole theory is somewhat lack of reasoning, the postulates and assumptions...
  24. P

    What is quantum field theory and why was it developed?

    What is quantum field theory and why was it developed? What is its relation to quantum mechanics?
  25. M

    How to Compute the Little Group Matrix in Weinberg's QFT Trilogy?

    Hi. I am new to this discussion group, so forgive me if this is not the appropriate forum for this question. A friend of mine and I are going through the first volume of Weinberg's QFT trilogy. My question regards the first problem at the end of chapter two. I think I completely understand the...
  26. B

    Question about RG and scaling in qft

    In critical phenomena, we can enlarge the block size(momenta fluctuation) by Kadanoff transformation, say k \rightarrow bk (b<=1) , and scale the new Hamiltonian by k' = k/b, x'=bx to recover to the original block size. In QFT, similarly integrating out the high momenta produces the effective...
  27. T

    Ontological status of fields in QFT

    I am interested in the input from the physics community on quantum field theory. If each particle has an associated field of which they are manisfestations what causes a particle to arise from a field?
  28. S

    QFT Comments and discussions

    Jeff mentioned he thought a thread on this might be good, and I decided to start it here so the board wouldn't be entirely blue sky. I'll start with a question raised by Patrick van Esch on s.p.r. In the Peskin and Schroeder textbook, they develop the expansion of the wave &phi; in the free...
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