Field theory Definition and 554 Threads

Hi, I'd like to ask recommendation for a QFT book. I have seen several other recommendations on this forum, but hopefully I'll provide enough info so you guys can have more specific advice. Background: QM (Griffiths, some parts of Sakurai), GR (Carroll), some residue...

Has anyone else found the solution to Einstein's Unified Field Theory equation? = MJA

Hi there PF. I have recently been working on the Classical Unified Field Theory, and i want to ask, why the Einstein-Maxwell equations does not candidate for a Classical Unified Field Theory, since it incorporates both general relativity and electromagnetism, into a single formalism? I...

"virtual particles" in rigorous quantum field theory If I am not mistaken "virtual particles" are just a name someone put to some integrals that we use to calculate different things, and those integrals depends on the perturbation scheme and on the gauge selected, and they don't even exist in...

Consider q3 in this exam: http://www.maths.cam.ac.uk/postgrad/mathiii/pastpapers/2006/Paper48.pdf I reckon I can manage a good part of the rest of the question. Unfortunately, I cannot manage the very first bit (drawing the Feynman diagram) and this is preventing me from continuing! I...

Can someone explain to me "Locality" in field theory? I know that two fields have to commute at space-like separations so that observations don't affect each other at these separation. what about the thing where the Lagrangian can't couple fields at different locations and time, is it so...

We have the effective action which obeys \frac{\delta \Gamma[\varphi]}{\delta \varphi(x)}=J(x) where and we are told the stationary point, \varphi_0, of this action, \frac{\delta \Gamma[\varphi_0]}{\delta \varphi(x)}=0, corresponds to the vacuum expectation value. (This is out of my notes -...

Homework Statement Could someone please explain what is meant by the term: \partial_{[ \mu}F_{\nu \rho ]} Homework Equations I have come across this in the context of Maxwells equations where F^{\mu \nu} is the field strength tensor and apparently: \partial_{[ \mu}F_{\nu \rho...

Hi there! I'm attending an introduction to elementary particle physics and I came into this statement about the Dirac equation: "When an interaction is added (using the gauge principle) in a field theory, then some terms appear like: gBj where, g is the coupling constants, B is a bosonic...

Classical Field Theory without Force Has anyone seen how this has been approached?

Sometimes I find useful and more interesting to read a less rigorous textbook before tackling a reference textbook of a given subject. Having said that, I am looking for a book that introduces the ideas of quantum field theory in a relaxed way. This allows to grab the ideas and then formalize...

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.

I'm trying to go through the Reissner-Nordstrom solution to the EFE's and since I'm trying to do this correctly, I find myself running into trouble about how to define everything. I set my coordinates up as x^a = x^a(r,\theta,\phi,ct) Now, I need to use the fact that \nabla^b F_{ab} = 0 as I...

We know the background metric has the description; g_{\mu \nu}\sim\eta_{\mu \nu}+h_{\mu \nu} I would like to know what the physical meaning is of the difference then? h_{\mu \nu} - \eta_{\mu \nu} When I've read field theories describing gravitons, they are usually denoted as...

Could I get a rough explanation of the following? I know I would need a whole course in field theory to understand a proper explanation of the following, but could someone give me rough answers to what certainly are naïve questions? First, the Higgs particles are supposed to produce the masses...

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...

Hi, I have a problem in classical field theory. I have a Lagrangian density \mathcal{L}=\frac{1}{2}\partial_\lambda \phi \partial^\lambda \phi + \frac{1}{3}\sigma\phi^3 . Upon solving the Euler-Lagrange equation for this density, I get an equation of motion for my scalar field \phi (x), where...

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...

The effective action Γ[ϕ] for a scalar field theory is a functional of an auxiliary field ϕ(x). Both Γ and ϕ are defined in terms of the generating functional for connected graphs W[J] as W[J] + \Gamma[\phi] = \int d^dx J \phi , \quad \frac{\delta}{\delta J(x)} W[J] = \phi(x) Show - \int...

The following must be false, since if it were true we'd have proof of a unified field, but can someone tell me why: Why doesn't the fact that a quantum field, which by definition is infinite (correct me if I'm wrong), prove that there is essentially only one underlying quantum field? How can...

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 am studying EE and want to know more about electric and magnetic field theory in more detail probably at the Quantum level.i realized that studying physics will suffice that but i am getting negative feedback from others that it will be not good for my career,they are saying that these things...

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?

Hi guys, So I'm working on this project to simulate QCD using a computer using (hybrid) monte carlo. I follow the majority of what I've read thus far, though there are a few things I'm uncertain about. Firstly, the Wilson loop is often written as U_{P} and the invariant gauge action is...

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...