Gauge Definition and 685 Threads

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...

such as the "Lorentz gauge"

Hi guys! I'll go straight to my question.. how come the lorentz group is not the gauge group of general relativity but it is instead the two sheet SL(2,\mathbb{C}) covering of it?? Thanks!

What is the meaning of the local gauge transformation exactly?? These days I'm studying. [D.J. Griffiths, Introduction to Elementary Particles 2nd Edition, Chapter 10. Gauge Theories] Here the Section 3. Local Gauge Invariance, the author gives the Dirac Lagrangian, \mathcal{L}=i \hbar c...

Hi everyone! Two question for you (): 1) I know that General relativity may also be seen as a gauge theory, but which kind of gauge group is used there?? 2) In the gauge theory wiew the Christoffel symbols \Gamma^{\alpha}_{\mu\kappa} in the covariant derivative...

As you may guess from the title this question is about the covariant derivatives, more precisely about the difference between the usual covariant derivative, the one used in General Relativity defined by:\nabla_{e_{\mu}}=\left(\frac{\partial v^{\beta}} {\partial...

As you may guess from the title this question is about the covariant derivatives, more precisely about the difference between the usual covariant derivative, the one used in General Relativity defined by:\nabla_{e_{\mu}}=\left(\frac{\partial v^{\beta}} {\partial...

How to choose the "symmetrical gauge" for 2D triangular lattice under uniform magnetic field and staggered magnetic field?

10 moles of an ideal gas has a gauge pressure of 2 atm what is new T?? no clue [b]1. Homework Statement [/b 10 moles of an ideal gas has a gauge pressure of 2 atm and a temperature of 200 K. If the volume of the gas is doubled and the pressure dropped to 1 atm., what is the new temperature...

Homework Statement A large cylinder is filled with an equal volume of two immiscible fluids. A balloon is submerged in the first fluid; the gauge pressure in the balloon at the deepest point in the first fluid is found to be 3 atm. Next, the balloon is lowered all the way to the bottom of the...

Though I've learned gauge transformation for a while, I can't figure out why it is significance in describing fields? For example, why electromagnetic tensor has to be gauge invariant? What does it physically mean?

I am trying to understand the derivation of the covariant derivative in Peskin/Schroeder (chapter 15.1, page 483). This is the important stuff: n^\mu\partial_\mu\psi=\lim_{\epsilon \rightarrow 0} \frac{1}{\epsilon}\left[\psi(x+\epsilon n)-\psi(x)\right] Scalar quantity: U(y,x): U(y,x)...

It is well know that massless spin-1 gauge bosons have two spin states s³=+1 and s³=-1. There are two independent approaches how this can be shown: 1) via the representations of the Lorentz group for p²=0 2) via fixing / eliminating unphysical gauge d.o.f., e.g. via elimination of the...

Hi all, (Also - if anybody could tell me how to get the latex to work on this page that'd be very handy!) While not technically homework this is a problem I've found I'm stuck on during my revision. Any help would be greatly appreciated. Homework Statement "By demanding that the covariant...

Hi, first post here so be nice! I'd be interested to hear any input on a fairly minor point that I've come across with gauge fixing. Specifically, for a U(N) gauge group, how to show it is possible to fix A_\mu=0 for some coordinate (the specific example I'm using is lightcone gauge in...

This is exact copy from Griffiths Introduction to Electrodynamics 3rd edition page 421. This is regarding to information travel in space. In time varying situation, E depend not only on V, but on A also.

I 've been reading about Homotopy , homology and abstract lie groups and diff.forms and I would like to see those beautiful ideas applied on a Nonabelian Gauge Theory . Any recommendations for a textbook that apply these ideas to gauge theory ? Text books on particle Physics and QFT do not...

http://online.kitp.ucsb.edu/online/qcdscat11/ You can see it happening in these talks. For now it's just d=4 N=4 super-Yang-Mills and d=4 N=8 supergravity, but there is every reason to think that the relationships being discovered there will be extended (in more complex forms) to other gauge...

Design a circuit that uses a stain gauge to create a voltage related to the strain experienced by the gauge. The strain gauge should remain electrically isolated from the ground. The DC common mode voltage should be minimized. Only stain-related signal to be measured does not have any...

Hello, Two copper cables have the same Impedance and Voltage but different Gauge. Will they act differently? Application: copper cable assemblies used for internet. Both with 100 Ohms impedance and 3.3 Volts but they have different Gauges (24, 26, 28 and 30). Thank you in advance...

Hi! I have a process with multiple feynman diagrams where gluon propagators occur. When I use an axial gauge for the gluon propagator, do I have to use the same n-vector for every propagator? Following this I wonder whether I can use the same n-vector for every polarization sum in axial gauge...

Hello Friends, Kindly tell me the formula/values for the following: 1. Gauge Factor in the primary winding of a transformer with voltage 5 MVA 2. Voltage Drop in the Secondary Side of a Current Transformer with 100:5 Please help Thanks

I'm just beginning to learn about Feynman diagrams and wanted to make sure I've got the correct basic understanding of QED. This is what I believe to be true right now: QED allows us to describe the interaction between an EM field and light/matter. The QED vertex is composed of a photon and...

Please teach me this: For gauge symmetry fields,only one of any elementary subconfiguration of the whole configuration covers the all physics of the field.So we need to cut off the redundant configuration.It seem to me,in a loose sense,there is only one way to cut off the redundancy(the gauge...

Hi, Hope some one can help me with a problem I am working on: It involves working out: \frac{\delta L}{\delta A_\nu} of the following Lagrangian: L=\frac{1}{4}F_{\mu\nu}F^{\mu\nu} + \frac{1}{2} (D_{\mu} \Psi)^{*} D^{\mu}\Psi The solutions show that this is equal to: \frac{\delta...

Homework Statement I am reading through my introductory course notes, and am given a question I don't understand how to answer. A rectangular tank contains fresh water inside it to a depth of 0.5m. The tank is 1m long and .7m wide. a) calculate gauge pressure at the bottom of tank b)...

I have one question, which can be very simple, but i can't answer it. I have Wilson action for ordinary SU(2) gauge field. In all of the books I had read, the proof, that calculations in lattice theory is true - is equality the Wilson action in continuum limit to the continuum action. We use...

Hi everybody, i have a question concerning potential energy (in all its forms, which basically means all forms of energy except the kinetic one). The kinetic energy of a system is always well defined: in the rest frame it is m² (convention c=1), in a frame moving at a relative speed v compared...

A rectangular fish tank measuring .75 x .50 m is filled with water to a height of 65 cm. What is the gauge pressure on the bottom of the tank? So I'm pretty sure I use the equation P=densityxgravityxheight I know gravity is 9.8, but I'm not sure what height I should use considering it is...

Is the following formula correct? Suppose we work in a 4D Euclidean space for a certain gauge theory, \int d^4x~ \text{tr}\Big(D_i(\phi X_i )\Big) = \oint d^3S_i~ \text{tr}(\phi X_i) and, \int d^4x~\partial_j \text{tr}(\phi F_{mn}\epsilon_{mnij}) = \oint d^2S_j~ \text{tr}(\phi...

Why is there no gauge symmetry for spin-1/2 fields? Has gauge symmetry to be related to spin-1 fields/ particles? thanks

Hello, if someone could enlighten me I'd be most grateful. Also, if anybody could point me in the direction of some really good free resources that would be great too. Thanks.

Hello, I don't understand two steps in solution to the problem: I. Homework Statement Show that QED action is invariant under gauge transformation. II. Relevant equations QED action: S= \int{d^{4} x \left[\overline{\Psi}\left(i\gamma^{\mu} D_{\mu} -m \right)\Psi...

What does it mean by "independent"(in gauge fixing of EM field) In my textbook, it gives the Coulomb gauge \phi = 0,\nabla A = 0 and says they will kill two degrees of freedom of the four potential and leave two independent components. I understand \phi = 0 will kill one degree of freedom...