Gauge Definition and 641 Threads

Hi all! Long story short, my QFT class recently covered gauge equivalence in QED, and this discussion got me thinking about more general gauge theory. I spent last weak reading about nonabelian symmetries (in the context of electroweak theory), and I like to think I now have a grasp on the...

what does it mean when they say the Gauge "Sector" of SM? what other sectors are there? Thanks

How do (offshell) QCD ward identities look like in the axial gauge? How to derive them? The standard treatment of ward identities uses BRST symmetry in the covariant gauge. I don't know where I can read about the axial gauge version of the ward identities.

i'm reading 'gauge theories in particle physics' by aitchison (http://www.ft.uam.es/personal/hernandez/QFT/Aitchison--Gauge-Theories-in-Particle-Physics-Volume-1.pdf) and i have some questions: 1. middle of page 23 right before section 1.2.3 heading: he implies because of the spectroscopy...

1) In one thread I saw that a Lagrangian that comes from a gauge theory principle is capable to generate interactions, and that would be why we should work with gauge theories. Nevertheless, any lagrangian which have multiplications of diferent fields generates interactions (or am I wrong?) 2)...

How do Holonomies or ideas of closed-loops in Gauge Theory compare to the ordinary? What is its advantage and disadvantage? And how does it scale in the plausibility rating?

Please teach me this: Why in general speaking the mass of gauge boson particle is zero(except W,Z bosons)?Because if we consider the self-energy of the bosons,we might think of the mass of gauge bosons. Thank you very much for your kind helping.

I'm just curious, in the Coulomb gauge changes made locally to the scalar and vector potential fields are propagated instantaneously, classically we wave off this problem since the potentials aren't directly observable... except they are in Aharanov-Bohm. Presumably there's something that saves...

I understand the conceptual meaning of gauge transformation which "can be broadly defined as any formal, systematic transformation of the potentials that leaves the fields invariant". I understand for example the U(1) and S(3) gauge symmetry in Gauge Theory. But what is this got to do with...

A strain-gauge bridge is made up of four resistive elements, each element having an unstrained resistance equal to R, as shown in the diagram below. When a strain is applied to the bridge elements R2 and R4 increase in resistance by an amount ΔR, whereas R1 and R3 decrease by ΔR, where...

Hello I am looking to learn about Lattice Gauge Theory. I am already understand the general theory, (that is, defining fermions and gauge fields on lattice sites and links, respectively), but am having trouble intuiting the results of such calculations. As an example, the following is a...

I have some ideas of canonical transformation is, but the ideas behind gauge transformation is still eluding me.

Hi, I have been assuming something I never took the time to prove because it is beyond my scope so to speak. But I am on the path, rest assured. My question is, is it possible to describe correctly say, the color force, using a different gauge group, regardless of the difficulty? That is...

Water poured slowly from a teapot spout can double back under the spout for a considerable distance before detaching and falling. (The water layer is held against the underside of the spout by atmospheric pressure.) In Fig. 14-23, in the water layer inside the spout, point a is at the top of the...

Homework Statement I've attached an image of a dam. The problem reads as follows: The fresh water behind a reservoir dam has depth D = 15 m. A horizontal pipe 4 cm in diameter passes through the dam at depth d = 6 m. A plug secures the pipe opening. Find the magnitude of the frictional force...

I was wondering if anyone could explain to me where the 2nd order terms in the gauge transformation h_{\mu\nu}\rightarrow h_{\mu\nu}-\xi_{\mu ,\nu}-\xi_{\nu, \mu}-\xi^{\alpha}h_{\mu\nu, \alpha}-\xi^{\alpha}_{,\mu}h_{\alpha\nu}-\xi^{\alpha}_{,\nu}h_{\mu\alpha}[/itex] come from. The...

I hear the statement that global symmetries in the boundary field theory corresponds to gauge symmetries in the bulk. 1) Is this a generic statement that is expected to hold for all holography pairs? (Maldacena states this towards the end of his first lecture at PiTP2010, which was supposed to...

Homework Statement Scientists have found evidence that Mars may once have had an ocean .5km deep. The acceleration due to gravity on Mars is 3.71m/s^2. (a) What would be the gauge pressure at the bottom of such an ocean, assuming it was freshwater? (b) To what depth would you need to go...

Homework Statement Consider a non-abelian gauge theory of SU(N) × SU(N) gauge fields coupled to N^{2} complex scalars in the (N,N^{_}) multiplet of the gauge group. In N × N matrix notations, the vector fields form two independent traceless hermitian matrices Bμ(x) =\Sigma_{a}...

Hi all , How can I find lecture notes on ArXiv ? I was looking for lecture notes on Yang-mills theories treated in the language of differential geometry but didn't succeed till now . Can some one recommend me some good resource for it?

Sorry for the newbie question. Just slap me and direct me to the right post. I did some searches but couldn't find my answer. If a fundamental particle must exert one of the fundamental forces against another fundamental particle, are the appropriate gauges boson then created by the first...

I presented a way to derive Coulomb force via the canonical mechanism. One uses Coulomb gauge \partial_i A^i = 0 derives \Delta A_0 = -4\pi\,\rho which can be inverted formally A_0 = -4\pi\,\Delta^{-1}\,\rho and calculates the interaction term in the Hamiltonian density...

I have a technical question and at the time being I can't ask it to a professor. So, I'm here: If I try to quantize the vector field in the Coulomb gauge (radiation gauge) A_0(x)=0,\quad \vec\nabla\cdot\vec A=0. by imposing the equal-time commutation relation...

In the weak field approximation, g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu} If we make a coordinate transformation of the form [itex]x^{\mu'}=x^{\mu}+\xi^{\mu}(x)[\itex] it changes [itex]h_{\mu\nu}[\itex] to [itex]h'_{\mu\nu}=h_{\mu\nu}+\xi_{\mu,\nu}+\xi_{\nu,\mu}+O(\xi^{2})[\itex] I...

Here and then I read gauge symmetry makes theories renormalizable. Unfortunately I could not find a satisfactory explanation why that so is. Could someone shed some light? thanks

Hi, In Electrodynamics, one often state about the gauge freedom of the magnetic potential. And so, we may choose to impose for example the Coulomb gauge, where the divergence of the potential is zero. But, isn't this only true if there exist no changing electrical field, \frac{\partial...

Homework Statement So I'm having some difficulty with my QFT assignment. I have to solve the following problem. In three spacetime dimensions (two space plus one time) an antisymmetric Lorentz tensor F^{\mu\nu} = -F^{\nu\mu} is equivalent to an axial Lorentz vector, F^{\mu\nu} =...

I Suppose, need to choose a correct wire gauge for a lighting circuit, how to calculate it. Input load 12V Battery, load (two 100 W bulb), .Please clarify.

I was trying to understand the standard calculation of Einstein's A,B coefficients in quantum theory textbooks and I came across the following difficulty. In the calculation of transition probabilities, total wavefunction is expanded into eigenstates of time-independent H_0 and the expansion...

Consider the Wilson lattice action for a Yang-Mills theory with two parameters - color N and coupling g. 1) The strong coupling expansion on the lattice is given in terms of \beta = N/g^2 . But what is the other parameter of the lattice theory? Is it N? In that case, does the \beta-expansion...

Hello all ! My question: Does fibre bundles are necessary for describing gauge invariance in electromagnetic case? Or fibre bundles uses only for describing gauge invariance in cases of weak, electroweak and strong interactions? Thanks

Hi, Don't know if anyone can help me but have a bit of confusion with Srednicki ch75 p466 just above (75.55). I understand why in non-Abelian gauge theory we get extra factors Tr(T^aT^bT^c) and so on, but I don't understand why the P_{L}\to1/2 diagrams then end up with the extra factor...

Hello everyone, I have a question about wire gauges and choosing the right one. Anyway this is related to my job. Long story short, we have systems that are powered by solar batteries(which are recharged through solar panels). Anyway these batteries supply 12V DC to various different devices...

Professor forgive me it has been many years since my last physics problem, but I was looking at the pressure gauge mounted in a T fitting on our shop compressed air line, and how the reading dropped when various high cfm tools were in use. As I understand it the indicated pressure reflects two...

hi guys... i need ur help... i have to design a device that can sense a force in triaxial axis which are x,y,z. the straing gauge is located at x,y,z axis also. my problem is, for example if the force come from x axis,i don't want the y,z strain gauge sense the reaction, i just want x-axis...

Hi, excuse the funny title :). In his book on quantum field theory Zee says (pag 245, fouth line) that QED gauge symmetry follows from the conservation of the current j=ψ γ^μ ψ (with the bar on the first spinor). I'm confused because that current is the noether current resulting from the...

I have a project this year called "Is gravity a gauge theory?". From my understanding, it is. But I was wondering if someone could quickly explain to me the way/ways of showing this and perhaps some papers or books that would be particularly useful. Thanks.

Accurate distance gauge out to z ~ 4 alleged (AGN reverberation) Because AGN (active galactic nuclei) are so bright, it would be nice if we could tell their intrinsic luminosity or "wattage". Then it would be like having a "standard candle" to tell distance with, by seeing how less bright it...

If a Meson is a Hadron that contains a Quark and an Anti-Quark which are both Fermions then why are Mesons a type of Gauge Boson?

Is Ads/CFT correspondance the same as gauge /gravity duality?

What is meant by saying that the Goldstone-bosons are "eaten" by gauge bosons? I've seen this statement all over, but can't find a good explanation of what this actually means. Anyone care to shed some light?

I first thought of posting on cataloguing various Grand Unified Theory proposals, but that would be an enormous task, so I decided on something simpler: cataloguing proposed GUT gauge-symmetry groups. The unbroken Standard-Model symmetry is SU(3)C * SU(2)L * U(1)Y QCD: SU(3)C -- color...

Hello I'm trying to understand how much freedom one has to pick a gauge to use for gauge fixing a free EM field and if so, on what conditions that freedom depends. Is there a particular reason (besides Lorentz covariance) to pick the Lorenz gauge? Are the alternatives (R\xi for instance) still...

In electrodynamics, the gauge potentials are not directly measureable, but components of the field strength tensors, which are the electric and magnetic fields are. But why are the electric and magnetic fields, the components of the curl of something not-measureable (the gauge fields)...

The gauge fields in Yang Mills theory are matrices: A_{\mu} = A^{a}_{\mu} T^{a} But A^{a}_{\mu} are vector fields, i.e. a=1,..,n four-vectors. Should not there be a U(1) gauge symmetry for each of them in addition to the non-abelian gauge symmetry? In Lagrangian for the strong force...

I have three questions which I have to put into context, much of which is paraphrased from a book by Kerson Huang. In QED, the source of the gauge field (is the gauge field different from the vector potential?) is the current and charge density j, ρ. When a particle (electron) couples to...

Homework Statement What reading will we see on a pressure gauge that is at the middle and bottom of a fluid column? and why Homework Equations P=pgh where p is density and P is pressure The Attempt at a Solution Well according to the equations as the gauge drop lower and lower it...

Hi there: I was just searching about Gauge theories and stuff and I find it very confusing. My major complication is the classification. I'd like you to tell me some definitions and construct a "family tree". I guess it goes something like this: Gauge Theory: A Field Theory in which the...

Can two Bosons 'collide' in the same sense as the Fermions (Since Pauli's exclusion principle is not applicable for Bosons)? The Leptons have anti-leptons (positron, anti-muon, anti-tau and three anti-neutrinos). Each of the 6 Quarks have their corresponding anti-quark. So, do the gauge bosons...

Hi, I have a question about the static gauge in string theory, in which one sets \tau = X^0 I understand that in the usual approach for strings in a flat target space, after the gauge fixing of the worldsheet metric gamma, \gamma_{\alpha\beta} = \eta_{\alpha\beta} one...