Quantum field theory Definition and 587 Threads

Pls. answer in the simplest and the most intuitive way. 1. What is the reason our quantum field theory needs perturbative approach. Is it because in the concept of fields, there is an infinite number of freedom in the oscillations of the virtual particles, or is it because the field is...

It's not a requirement at my school's Physics PhD program (it's a graduate-level pass/fail course), so I'm curious as to whether or not other schools have the requirement, and how many students ultimately opt to take it.

From a previous post, I now know that the 'qualities' of QM such as entanglement, superposition of states, decoherence, measurement problem, are still with us in QFT. 1. Is the Dirac equation the primary equation in QFT? 2. What equation governs the evolution of a macroscopic object in QFT...

Please teach me this: Why we do not call the quantum field theory the quantum mechanics of a changeable number particles.Why we must use the term ''field''.I think that the indistinguish of identical particles,the dual particle-wave and changeable in number of particles mean the ''expansion''...

Steven Weinberg wrote: ''In its mature form, the idea of quantum field theory is that quantum fields are the basic ingredients of the universe, and particles are just bundles of energy and momentum of the fields.'' (see p.2 of his essay, ''What is Quantum Field Theory, and What Did We Think It...

Mark Srednicki's "Quantum Field Theory" I just wanted to know what level the book QFT by Mark Srednicki is, that is... Is it considered first year Masters, second year masters... Low PhD..?? I know it's not upper year undergrad, that's for sure. Just wondering. thanks!

Quantum Field Theory Purly in Momentum Space? Hello, I have a complicated nonlinear-nonlocal-nonrelativistic-effective action in momentum space and would like to do perturbation theory with that. I need to find propagator and Feynman rules. I can not go to x-space and follow the standard...

I'm trying to understand path integrals as described in my lecture notes (which are reinforced by Peskin &Schroeder). Anyway on p284 of P&S, there is a formula inbetween eqns (9.17) and (9.18) that reads: e^{-iHT} | \phi_a \rangle = \sum_n e^{-i E_n T} | n \rangle \langle n | \phi_a \rangle...

Please teach me this: Can we demontrate the convergence of perturbation series of quantum field theory(Feymann diagrams) after making the renormalizing procedure? If we can't demontrate that,why we still consider the perturbative method using in quantum field theory being useful and believable...

Dear all, I am taking 'field theory' course this semster and I am reading 'quantum field theory' by mandl and shaw. In chapter 8, equation (8.9) we see: E_1 E_2 v_rel=〖[(p_1 p_2 )^2-m_1^2 m_2^2]〗^(1/2) and we know that as p is a four vector: p=(E,P)=m so p_1 p_2 = m_1 m_2 ! Isn't...

What is a good to book to start reading about quantum field theory?

I wish to learn quantum field theory? Where should I start? I do know something about Dirac's bra-kets and elementary QM.

Does anyone know why in quantum field theory mass terms are quadratic in fields (not contaning derivatives)? Thanks!

Hi I am looking for a book or pdf where I can read more about quantum field theory. How to renormalize and find the counterterms. thanks alot

Hi guys, Before responding to my post, please note that I am only familiar with the mathematics of nonrelativistic quantum mechanics, and don't know any quantum field theory. All I have is this vague idea that quantum field theory is the union of special relativity and quantum mechanics...

what is the analogue of 'space is curved' in Quantum Field theory ?? if in General Relativity the main issue is that 'space is curved' what is the equivalence of it in Quantum mechanics ?? , for example how can QFT describe the curvature of space ??

Does anyone know of quantum field theory lecture videos besides susskind and coleman.

can zeta regularization provide FINITENESS to quantum field theory ?? recently i came across (google) these papers http://vixra.org/abs/1003.0235 http://vixra.org/abs/1001.0042 http://vixra.org/abs/1001.0039 using the zeta regularization algorithm plus analytic continuation he...

I have pretty good handle on non-relativistic quantum mechanics, but I would like to learn about the Standard Model (Quantum Field Theory). What is the best introductory book and/or introductory article on QFT? Thanks Here are some I've heard of: Articles "[URL Model: An Introduction Authors...

The in the preface to his quantum field theory book, Srednicki mentions that there is a set of lectures by Ed Witten on quantum field theory for mathematicians that is available online. Does anyone know where this is?

Quantum Field Theory -- variational principle In non-relativistic quantum mechanics, the ground state energy (and wavefunction) can be found via the variational principle, where you take a function of the n particle positions and try to minimize the expectation value of that function with the...

This may be a very basic question, but I've had now some background on the quantum theory, and I think I am missing something. Roughly speaking, I feel like the main difference is that quantizing involves going from field amplitudes to counting operators, implying that a quantum process involves...

Homework Statement Here is equation (2.68) (M^{ij})_{ab} = -i(\delta^i_a\delta^j_b - \delta^j_a\delta^i_b) Here is equation (2.69) (abbreviated) [M^{ij},M^{lm}]_{ab} = +i\delta^{jl}(M^{im})_{ab} +- ... The problem is to show that (2.68) implies (2.69) Homework Equations The...

At least one of us at this discussion board has expressed an interest in fractal modeling of spacetime, or of dynamics.* This paper by Calcagni may be suggestive of what form such an approach could take. http://arxiv.org/abs/1001.0571 Quantum field theory, gravity and cosmology in a fractal...

Research in relativistic quantum mechanics proves, through a series of no-go theorems, that localized three (or four) dimensional particles cannot be the basic elements of reality. It is claimed that a field ontology can explain the appearance of three dimensional particles, but this new idea...

Hi there, I am currently studying Quantum Field Theory (well, for about 3 weeks isch), and it's really interesting and good fun! However, I would like to know how QFT relates Integrable QFT... I don't really know what it is. Can anyone tell me (i) The theoretical background of Integrable...

Hi there, I am currently studying Quantum Field Theory (well, for about 3 weeks isch), and it's really good fun! I would like to know how QFT relates Integrable QFT... I don't really know what it is. Can anyone tell me (i) The theoretical background of Integrable QFT (ii) The...

Hey everybody, since the previous thread got locked I thought I would open this thread as a place to discuss rigorous issues in quantum field theory, be it on the constructive or axiomatic side of things. I apologize if one is not supposed to start a discussion with posts from old threads...

i need references on the topics. thanx

I have a few questions about this. My understanding is this: In the canonical approach to QFT there is an ambiguity in the order in which we write operators when calculating matrix elements. The different choices just correspond to different vacuum energies, which we are free to ignore since...

What are some good books for non physicists on quantum field theory?

For free quantum fields, there are two types of observables indexed by wave-number, \tilde{\hat{\phi}}(k), the Fourier transform of the local field, which can be written as a(-k)+a^\dagger(k), and projection operators such as a(k)^\dagger\left|0\right>\left<0\right|a(k), a(k_1)^\dagger...

Please let me know what lecture I have to previously take. I already took undergraduate level lecture of quantum mechanics and mathematical physics. And I also want to know that perturbation and scattering theory is hardly important on studying QFT..I'm so worry about that I didn't study...

Hi all, I bought a book recently of this title. I wanted this one to compliment the field theory book I have already (Peskin and Schroeder) because I find the latter a little hard to follow on my own (I am currently taking Relativistic Quantum Mechanics and will be taking QFT course at some...

I have a fairly good background in mathematics (algebra, analysis, topology, differential geometry)... and a good physics background (till QM, general relativity). I am looking to study Quantum Field Theory on my own. I do not intend to master QFT completely and all its techniques, but want to...

I have a question about an equation in Maggiore's Modern Introd. to Quantum Field Theory p.52: \delta x^\mu = w^\mu_\nu x^\mu = \sum_{\rho < \sigma} A^\mu_{(\rho \sigma)} w^{\rho \sigma} where the A is defined as A^\mu_{(\rho \sigma)}=\delta^{\mu}_{\rho}x_\sigma - \delta^\mu_\sigma x_\rho...

In quantum field theory a field is described by a multiparticles state? And, a single particle is itself a field?

I'm not sure if this post should go here or into the quantum physics forum, but I figure this can't be a bad place to put it. I have a few questions about canonical quantization and quantum field theories with interactions that I hope someone can answer. 1. I've been told that in Klein-Gordon...

Hi all, I have a question about the formulation of quantum field theories in curved spacetime. I'm still learning, and so I might not articulate this very well, but I'm wondering: If a region of spacetime can warp and curve, dynamically changing its shape in response to changes in energy...

Hello Physics Forum I will be taking a quantum field theory course next semester. I bought Mandl's book and Zee's book and looked them a bit. I have also been talking to others that have taken the class in previous semesters. I have a general idea of the failings of nonrelativistic...

\frac{1}{x-i\epsilon}=\frac{x}{x²+a²}+\frac{ia}{x²+a²}= P \frac{1}{x}+i pi \delta(x) P means the principal value, a is possibly infinitesimal (?), i is the imaginary unit Where does the pi, Dirac delta come from? What principal value? It is from a quantum field theory book.

The question is as follows; 'A free quantum field theory is related to an infinite number of quantum mechanical harmonic oscillators as unit mass particles on springs with spring constants k, where k takes all values. Now imagine the following scenario: these particles also have non-zero...

I will be applying for grad school this Winter, but from January 2009-September 2009, I will be done with any course work and will not have any money to commute to my school to continue to do research. So I figured it would be a good opportunity to go further in my mathematics and physics...

When I read the security report from Cern (not that I am too worried), I came to something, which I do not fully understand: As we all know, we are save from micro black holes created at the LHC because of Hawking radiation (for one of many reasons). The Cern people push this argument further...

Hi I was wondering if anyone has a good introductory article about QFT applied to condensed matter physics. I know a bit about condensed matter physics, and a bit of QFT applied to particle physics. thanx

i've read that quantum field theory can be applied to condensed matter physics but i don't understand how: quantum field theory is the union of SR with QM but how is SR related to condensed matter physics? i understand that quantum field theory would be useful because it can describe...

I am trying to search for the first person who introduced group theory into quantum field theory.

"FIELDS" by: WARREN SIEGEL C. N. Yang Institute for Theoretical Physics State University of New York at Stony Brook Stony Brook, New York 11794-3840 USA http://insti.physics.sunysb.edu/~siegel/Fields3.pdf

[SOLVED] Quantum Field Theory: Field Operators and Lorentz invariance Hi there, I am currently working my way through a book an QFT (Aitchison/Hey) and am a bit stuck on an important step in the derivation of the Feynman Propagator. My problem is obviously that I am not a hard core expert...

Non Commutative Cross-Section hello, this is my first post here, i have searched the web but i didnt find what i am looking for,so i hope i find it here. i am looking for the formula of the cross section of compton scattring in the non commutative space-time .