Field theory Definition and 523 Threads

I am getting apparently conflicting statements about the conformal transformation law of the vertex operator appearing in and 2D QFT (such as in bosonic string theory). For example, according to http://en.wikipedia.org/wiki/Conformal_field_theory" (eqn 64 on page 15), the transformation law is...

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...

In field theory, the commutator of two fields vanishes at space-like separations. The explanation given is microcausality, which means that things separated farther than light can travel, cannot influence each other. However, the Green's function does not vanish at space-like separations...

Hello fellow physicists! I'm currently trying to learn some QFT and the reader gives an introduction by expressing the non-relativistic hamiltonian with integral and creation, destruction operators. Later he writes: |Psi, t > = \int d3x1...3xn Psi(x1, ..., xn; t) a+(x1) ... |0> And...

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...

Hi It is know that the colour exhibited by coordinate compound is because of d-d electron transitions. These d-d transition lead to absorption of photons of a paticular frequence. AND when a electron become exited due to absorption of photon it should radiate electromagnetic wave of frequency...

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

Hello, I'm looking to get a book on classical field theory at a beginner level, so please don't recommend anything that a first year grad student wouldn't understand! Anyways I was look into getting Landau and Lifgarbagez's book any other suggestions? I don't really have any idea of which...

Homework Statement Given the the Lagrangian density L= \frac{1}{2}\partial_\lambda\phi\partial^\lambda\phi + \frac{1}{3}\sigma\phi^3 (a)Work out the equation of motion. (b)Calculate from L the stress tensor: T^{\mu\nu}=\frac{\partial L}{\partial(\partial_\mu\phi)}\partial^\nu\phi -...

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

Hi everybody, I'm not entirely sure if this should be posted here or in the Quantum Physics section, if a moderator feels it would be more suitable there, please feel free to move it. As the title indicates, I'm a mathematics Ph.D student (studying Vertex Operator Algebras) and I'm interested...

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

I have a mathmatical formula that ties gravity to the electromagnetic force,how can I present it without someone with more credentails stealing the credit

Hello folks, I would like to know more about the standard books in Classical Field Theory which I am not really familiar with. I would be grateful if you suggest something (be it a book/lecture notes etc...) in line with the 2nd chapter of the following lecture notes...

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...

I remember when I learned some basic continuum mechanics, Lagrangian is just a integral of lagrangian density over space, which is quite easy to accept because it's just a continuous version of L=T-U. Now I'm trying to start a bit QFT and notice that Lagrangian is an integral over space-time...

I'm looking for a book that describes Quantum Field Theory from a group theory approach for mathematical physicists (with emphasis on the physics part). Ideally I want it to first describe and define groups, representations and irreducible representations. The more rigorous the math, the better...

The workshop starts tomorrow. Should be very interesting. http://www.physics.ntua.gr/corfu2010/nc.html The programme is online http://www.physics.ntua.gr/corfu2010/Program/4thSession.pdf M. Reuter and M. Henneaux will talk about "Running Immirzi Parameter and Asymptotic Safety"...

I know little about these issues, so my questions may be dumb. 1. Do exact solutions exist for non-Abelian gauge theory without matter fields? 2. Do exact solutions exist for Abelian/Non-Abelian theory with matter fields (scalar or spinor)? 2. Are solutions well-behaved? I'm asking because no...

I'm working on a "draw all possible Feynman diagrams up to order 2" problem for a scalar field that obeys the Klein-Gordon equation, and I'm wondering about a few things. When I did a course on particle physics and was first introduced to Feynman diagrams in the context of QED (but not QED...

MTd2 spotted this one. It was time for a paper like this. Very glad to see it. http://arxiv.org/abs/1008.0354

"No prior geometry" and the group field theory vehicle Atyy recently pointed us to a provocative quote from MTW: Mathematics was not sufficiently refined in 1917 to cleave apart the demands for "no prior geometry" and for a geometric, coordinate-independent formulation of physics. Einstein...

The question is more of a mathematical question then one about physics in the attached file between equations 6 and 7 it says "integration over the modes" i don't know how they go from the integration measure \int D\phi \rightarrow \int D\phi_1 D\phi_2...D\phi_N any advice would be...

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 ??

wikipedia says http://en.wikipedia.org/wiki/Group_field_theory Overview Group field theory is a theory of quantum gravity. It is closely related to background independent quantum gravity approaches such as loop quantum gravity and spin foam and causal dynamic triangulation. It makes...

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

Hi, could anyone explain to me why in effective field theory (as in ch29 srednicki), you look at diagrams with only k<\Lambda as external lines and k>\Lambda for your interal lines? why do these diagrams with say, 6 external legs of this type, equate to the constant c_6 say? In previous...

Can anybody suggest a good introductory book on CFT. I would like to learn String Theory; and this is my basic motivation to learn CFT...

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...

Hi, I was looking for a book that would explain classical field theory in a Hamiltonian setting. What I mean by this is that there be no *actions* around, no *Lagrangians* and *Legendre transforms* to define the Hamiltonian and so on. What I'm looking fo is an exposition of (classical) field...

I know that the classical picture of QED is Coulomb interaction, magnetic interaction etc. But what does the classical phi^4 theory look like? In particular, do particles attract or repel each other in this theory? P.S. I'm surprised that my field theory books never discuss this. (At least in...

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...

What is the reasoning for saying that the scattering matrix in quantum field theory is unitary? Take the initial state to be an electron and a positron. All sorts of crazy products can result in the final state, from photons to Z's to Higgs to an electron/positron with different momenta, to...

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...

i have been given a problem for writing s matrix in second order perturbative theory for an interaction hamiltonian with phi 4 and phi 3 contributions. it is also given that our initial state is of 2 particles and final state is of three particles. now in solving that i have to take time...

If I take the massless limit of a massive field theory (e.g. considering cross-sections or other observables), do I always obtain the "right" massless theory?

I've been sick with mono for the past month and am trying to catch up in my Algebra class, but being so far behind I'm having a lot of trouble trying to grasp so much in so little time. Currently, I'm trying to get my head around field theory. Here are are few problems I've been working on. Is...

I've been sick with mono for the past month and am trying to catch up in my Algebra class, but being so far behind I'm having a lot of trouble trying to grasp so much in so little time. Currently, I'm trying to get my head around field theory. Here are are few problems I've been working on...

When people give the rules for the operator product expansion of fields in CFT, they always give the rule for the OPE of a product of two fields. But let's say that we have three fields. To be specific, consider the OPE of T(z_1) T(z_2) \Phi(z_3) where T is the energy-momentum tensor and \Phi...

Hi, Can someone briefly explain Field theory to me? Ie, in this book, it says that 1+1 = 0 when field : F (subscript 2) And you can create a finite field for any prime number p. I don't understand this lol. I also got this table: + 0 1 2 3 0 0 1 2 3 1 1 0 3 2 2 2 3 0 1 3 3 2 1 0...

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...

Hi there, Can anyone explain to me what Conformal Field Theory really is in brief summary? I do not mind if anyone wants to go into technical details as I have some basic knowledge of quantum field theory already. Thank you