Quantum field theory Definition and 558 Threads

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...

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 .

I am to produce a research presentation for a class of Masters' physics students on the casimir force, going via a detailed treatment of the vacuum effects in conducting cavities, going on to explain some real phenomena and applications. What I am after is a good introductory text on quantum...

Homework Statement A. Zee Quantum Field theory in a nutshell, p. 31. There is painfully little explanation on this page. I'm okay with the action: S(A) = \int d^4 x \mathcal{L} = \int d^4 x\{ \frac{1}{2}A_\mu [(\partial^2 +m^2)g^{\mu \nu}-\partial^\mu\partial^\nu]A_\nu + A_\mu J^\mu \}...

Quantum field theory or particle physics what first? Hi at present I am confused whether i should try obtining a firm conceptual understanding of QFT before jumping to particle physics or whether aa very brief overview of QFT is enough ?

Since I'm very interested in General Relativity and Quantum field theory, I'd like to start a doctoral program abroad after my master study (I'm studying in Switzerland and will get my master degree in approximately 1.5 years). I was surfing around in the internet and found for example the...

I was wondering what to read for quantum field theory and in what order if applicable: I have "qft in a nutshell" by zee, "intro to qft" by peskin, "qft" by rydern, and "advanced qft" by sakurai.

Hi, I am curious about the following and I aim these questions to the people who do general relativity and uantum field theory over there. What is the difference between field theory of general relativity and field theory of quantum field theory? Is the former only for study of gravitation...

I was wondering if anybody knew any good books that give an easy to understand quantum field theory. I am talking from a view point of a person who has read the third volume of the feynman lectures and quantum mechanics demystified. if this is not enough to even start a easy to understand...

I know that the vacuum in Quantum Field theory is not empty, but sometimes I find some people say that the particles are created from nothing because they are created from the vacuum , are those people expression a misleading?

On this forum, quantum field theory (QFT) is a part of this subforum (Quantum Physics), while particle physics is a subject of another forum. These two topics - QFT and particle physics - are clearly separated. On the other hand, most textbooks on QFT are also textbooks on particle physics...

In my recent paper http://xxx.lanl.gov/abs/0705.3542 entitled "Is quantum field theory a genuine quantum theory? Foundational insights on particles and strings" I argue the following: Practically measurable quantities resulting from quantum field theory are not described by hermitian...

http://sites.google.com/site/winitzki/" a draft of an introductory textbook on quantum field theory in curved spacetime - free quantum fields in expanding universe, Unruh effect, Hawking radiation, also Casimir effect and some basic stuff on path integrals and effective action. The book is not...

I don't understand how Peskin & Schroeder can evaluate the integral on page 27 by having the real axis wrapping around branch cuts just like that. The picture of the contours are on page 28.

hi everyone, There are so many books about QFT, but what is in your oppinion the best book to learn quantum field theory?

Hi all. I'm running a thread in the Philosophy section about rules of the universe etc but I'm stuck on a fundamental question which probably only a current quantum mechanics expert can answer. In essence do the most current iterations of QF theory maintain that the ultimate and irreducible...

Hi,there! I want to study Quantum Field Theory but I don't know what book to use! I have a rather good background in quantum mechanics and electrodynamics, and I probably can gain access on the following books: Brown L.S. : "Quantum Field Theory" Peskin and Schroeder : "Introduction to Quantum...

I'm interested in teaching myself QFT. My BSc is in Mathematics and Physics, so I probably have a stronger mathematical background than the average physics graduate. However, I'm assuming it's almost certainly not good enough. What I am looking for is a way of sensibly teaching myself the...

U = e^{\frac{1}{2} B} = \cos(\frac{1}{2} \theta) + b \sin(\frac{1}{2} \theta) we can then write: U = e^{\frac{1}{2} \theta b} = \cos(\frac{1}{2} \theta) + b \sin(\frac{1}{2} \theta) And if we rely on Joe's expression, r=\frac{\theta}{2} (rotor angle is always half the rotation): U = e^{br}...

Let be the nuclear reaction: ee \rightarrow e+e+ (if not possible a similar one) Of course we have 2 states |A> with 2 electrons and |B> with two "positrons"..if we wished to compute the transition probability we should know: <B|S|A> where "S" is the S-Matrix..my question is..is...

As I read in my quantum mechanics book the delta function is sometimes called the sampling function because it samples the value of the function at one point. \int {\delta (x - x')} f(x')dx' = f(x) But then I opened a quantum field book and I found equations like that: \phi (x) =...

if we know that the divergent series in perturbation theory of quantum field theory goes in the form: \sum_{n=0}^{\infty}a(n)g^{n}\epsilon^{-n} with \epsilon\rightarrow{0} then ..how would we apply the renormalization procedure to eliminate the divergences and obtain finite...

Hi, I'm a little confused about the nature of fields in quantum field theory. I sometimes see people make reference to an "electron field" or other matter field of some sort, and in my understanding, in quantum field theory, ALL the different fundamental particles can be represented as...

Can anybody recommend some good quantum field theory books for introduction to the subject? I am already familiar with some of the techniques from applications to statistical mechanics, but I would like to see them in a different context.

Why do theories of superconductivity need to be quantum field theories with 2nd quantisation? Isn't first quantisation enough?

Greetings--I have a few questions from An Introduction to Quantum Field Theory by Peskin and Schroeder. Note: I'm not sure how to construct the contraction symbol using \LaTeX, so instead I will use the following cumbersome convention: \overbrace{\psi(x)\overline{\psi(y)}}=S_F(x-y), they...

At my physics faculty there is this magazine that comes out once every three months. I wrote an article about GR for it. Introducing not only the concepts but also some mathematics. I explained the field equations and derived some implications of the Schwarzschild metric. I could do this because...

Hello All, Hendrik van Hees just started a qft course. Here's his announcement: We just started an online qft theory course, reading along Zee's textbook. Soon, it will be provided as a an online course at the supersymmetry web page: http://www.superstringtheory.com/ Since the...

One question has disturbed me long time, I don't know the distinction between quantum electrodynamics and quantum field theory. By the way, which quantum field theory or quantum electrodynamics textbook is prefer?

In short, the question is, how is the position operator related to the position-parameters of a quantum field ψ(x)? For instance, consider a quantum-mechanical state of two particles |Ψ>. This can be expanded in terms of the position eigenstates |x1,x2> to give the position representation...