Gauge Definition and 641 Threads

Coulomb gauge fixes gauge by setting div(A)=0. What has it to do with adding a gradient to A and subtract a partial time derivative from V?

I would like to hear an original explanation of gauge symmetry. What gauge symmetry really means and why it is needed to describe nature. I am more or less familiar with the standard treatment of electromagnetism and Yang Mills theories from QFT texts, but feel still unsatisfied since I have...

I have a question regarding gauge invariance. When a charged field changes phase: y -> e^it * y The electromagnetic field adjusts to make the equations work: A_m -> A_m - idt / dx_m What I don't understand is why, purely from a physics standpoint, this would happen? That is, is...

Hi there, How is the light-cone gauge useful for a quantum relativistic particle and for a quantum relativistic string? Why is it important that the light-cone gauge is used? Does it actually simplify the mathematics a lot? Thanks

If we consider the following Lagrangian: L = m * (dot x)^2 / 2 - e A dot x - e phi with A the vectorpotential and phithe scalar potential, then the Euler-Lagrange equations, reduce to the known formula of Lorentz-force: m ddot x = e dot x X B + e E know, this equation is invariant under...

Is anyone familiar with any resources on the study of continuity of functions on the real line via gauges? This is inspired by the gauge integral. Briefly, a gauge on a closed and bounded interval I \subseteq \mathbb{R} is a strictly positive function \delta : I \rightarrow \mathbb{R}. Let...

1. Problem Statement: I am trying to measure the radial (#s 3-6) and hoop (#s 1, 2, 7, 8) strain (and from that, stress) present in an aluminum cylinder. I am trying to use a standard full wheatstone bridge setup, but am having trouble settling on a setup that would give me an accurate...

In standard, old-fashioned, Kaluza Klein theory we have new dimensionful parameters, the size of the compact dimensions, but they become dimensionless after quotient against the Plank size, so they become the adimensional coupling constants of the gauge groups associated to the symmetry of the...

Hello: The gauge symmetry of the standard model is written in authoritative places like wikipedia :-) as U(1)xSU(2)xSU(3). This would have 12 elements in its Lie algebra corresponding to one photon, W+, W- and W0 or Z, and the 8 gluons. I recall reading discussions that such a...

Homework Statement I want to show explicitly that the Lagrangian... L_\Phi = (D_\mu \Phi)^\dagger (D^\mu \Phi) - \frac{m^2}{2\phi_0 ^2} [\Phi^\dagger \Phi - \phi_0 ^2]^2 where \Phi is a complex doublet of scalar fields, and D_\mu = (\partial_u + i \frac{g_1}{2} B_\mu) is the...

A. Garrett Lisi, L. Smolin and S. Speziale, “Unification of gravity, gauge interactions and Higgs bosons in the extended Plebanski formalism,” to appear. This interesting reference was found in a recently posted preprint by Smolin and Speziale. (thanks to MTd2 for spotting the Smolin...

According to Steven Weinberg ('The quantum theory of fields', vol.1), the principle of gauge invariance stems from the fact, that one cannot build the 4-vector field from the creation/annihilation operators of massless bosons with spin >= 1. This '4-vector field' ('vector potential'), if we...

I'm sorry if what I say is not right, or I haven't understood it right, - In 3+1 D we have the photon with spin 1 => it has two polarizations. Our Gauge field A_\mu has 4 components => We have two extra degrees of freedom. => We need to get rid of the extra 2 fixing the gauge. 1. The...

Homework Statement What is the gauge pressure at a depth of 100 m. in water?Homework Equations Pgauge = rho*g*h (or the pressure above atmospheric pressure)The Attempt at a Solution I missed a day of class (and on a summer class, that's a LOT of material). I am working problems that are...

Homework Statement For experimental validation of a design based on FEA, a prototype was tested using strain gauge rosettes at critical locations in a typical t-delta configurations, consisting of 3 gauges: A, B, C and fourth (extra) gauge D. D normally serves as a check on the strains recorded...

What is "gauge" in General Relativity? I am trying to concoct a dumbed-down explanation of the significance of gauge in physics (and especially in General Relativity (GR)) that my limited intellect can cope with. I need some serious correcting about how to unravel the differences between...

I know that there are many reasons why SU(2) can't be the electroweak gauge group, but I want to have some clarifications about the following one, that disergads neutral currents: in this case the currents are (considering only the lepton sector of the first generation)...

The superpotential is basically a product of left chiral superfields, taking the \theta \theta component. However, under a supergauge transformation, the left chiral superfields change, and the superpotential does not seem to be supergauge invariant. In fact, under supergauge...

Homework Statement Water flows at 3.64 L/s through a horizontal pipe that narrows smoothly from 10.2 cm diameter to 4.89 cm diameter. A pressure gauge in the narrow section reads 47.0 kPa. What is the reading of a pressure gauge in the wide section? Homework Equations F=PA P1+...

Does "coordinate system" = "gauge"? [SIZE="4"]Are "coordinate system" and "gauge" the same thing? What about "coordinate transformation" and "gauge transformation"?

Recently I've been trying to understand the geometric formulation of gauge field theory. The mantra I've been hearing is that a gauge field is a connection for a principal bundle where the structure group corresponds to the gauge group. Fields which are charged under the gauge group form...

Homework Statement Determine x and y strains in order to construct a Mohr's circle of strain. A 2-gauge Wheatstone (the third/middle gauge was not working), with gauges 90-degrees apart, was attached to a specimen steel plate 15-degrees offset from the x and y axes. An axial load was applied...

A strain gauge has a unstrained resistance of 120 ohms, gauge factor of 2.0 is connected to steel girder so it experieces tensile stress. If strained resistance of gauge is 120.13 ohm. How do i calculate the tensile stress value? I have looked all over the internet for equations relating but...

A strain gauge has a unstrained resistance of 120 ohms, gauge factor of 2.0 is connected to steel girder so it experieces tensile stress. If strained resistance of gauge is 120.13 ohm. How do i calculate the tensile stress value?

Given a set of a scalar function V and a vector function, how does one recognize that it is a coulomb gauge or lorentz gauge transformation? Actually there is a method that i use but i am not sure if it is always true: what i do is to make an electric field (from that set and using known gauge...

Homework Statement I'm just working through a textbook and there's a line in which I'm clearly missing something. What I want to do is show that from: [tex] \bar{h^{TT}_{\mu \nu}} = A^{TT}_{\mu \nu} cos(\omega (t-z)) [\tex] to [tex] h^{TT}_{\mu \nu} = B^{TT}_{\mu \nu} cos(\omega (t-z))...

Quick question. If particles that mediate interactions are called gauge bosons, why isn't Pion considered a gauge boson. I'm pretty sure I've come across a few interactions mediated by it.

I apologise if this question has been asked before, but I coudlnt find it, so: Is there some deeper reason for demanding gauge invariance other than that it allows us to include interactions between the gauge field and the fermions? I have seen people claim that it is "in keeping with the...

The problem I am working on states that I have a power factor of .5, a real power of 3600 watts, a voltage of 240 V, and a distance between a motor and transformer of 100 feet. Im trying to find the Minimum wire gauge that could be used... Do I need to find the current and than go to...

1. Homework Statement Water at a gauge pressure of 3.8 atm at street level flows into an office building at a speed of 0.80 m/s through a pipe 5.4 cm in diameter. The pipe tapers down to 2.6 cm in diameter by the top floor, 20 m above (see figure here...

Hi, my group and I are doing an experiment on forces experienced on a baseball. Our setup involves the baseball attached to a motor, which is coupled to a cantilever beam (1/2 inch thick, 7 inch long aluminum rod). The beam has a strain gauge attached to it and we are recording data with...

I understand the concept of a gauge transform, and I understand why it is that the magnetic field would be unchanged with the addition of the gradient of an arbitrary scalar potential onto the magnetic vector potential A, and I understand why the electric field E would be invariant under the...

I assume I am making a mistake here. Can you please help me learn how to fix them? In electrodynamics, the gauge transformations are: \vec{A} \rightarrow \vec{A} + \vec{\nabla}\lambda V \rightarrow V - \frac{\partial}{\partial t}\lambda These leave the electric and magnetic fields...

The vector potential can be expressed in the following way: ∇^2 Ay-∂/∂y (∇∙A)=-μJy (Here only taking y components) Vector A is not determined uniquely. We may add derivatives of an arbitrary function (gradient) to the components of A, and the magnetic field does not change (curl of...

This is a very good little tutorial on how to use strain gauges and the tradeoffs found by using different sizes. http://www.abacus.co.uk/jkcm/cache/fl0008816.jpg http://signalprocessing.prosig.com/FatigueTesting/strain-gauge-close.jpg[/URL]...

The main water line enters a house on the first floor. The line has a gauge pressure of 2.00 x10^5 Pa. (a) A faucet on the second floor, 7.0 m above the first floor, is turned off. What is the gauge pressure at this faucet? P2= P1 + (density x g x h) (2 x 10^5)= P1 + (1000 x...

Hi everyone, This is my first post and I hope to get some better understanding of something that has been bugging me. I understand (global) gauge invariance in the sense that |\psi\rangle denotes the same (physical) state as e^{i\varphi}|\psi\rangle, or more generally, the physical state...

In classical e&m, for gauge invariance you can choose div[A]=0 or div[A]=dV/dt, where A is vector potential and V is the scalar potential; however, in qft you multiply your wavefunction by a phase factor that is dependent on space time. My question is that is there any parallel that can be drawn...

I am trying to find out which combination of wire loop diameter and thickness produces the most current. The problem with thin wire is obviously that it has a lot of internal resistance, but it is easier to wind in more loops. Does anyone know for a fact if a certain gauge/thickness is the best...

In a giraffe with its head 2m above its heart , and its heart 2m above its feet, the hydrostatic gauge pressure in the blood at its heart is 250 torr . Assume that the giraffe stands upright and the blood density is 1.06 * 1000kg/cubic metre.In torr find the (gauge) blood pressure at the brain.

Homework Statement The main water line enters a house on the first floor. The line has a gauge pressure of 1.70 X 10^5 Pa. (a) A faucet on the second floor, 5.2 m above the first floor, is turned off. What is the gauge pressure at this faucet? Pa (b) How high above the water main could...

hello all gauge symmetries are redundencies of the description of a situation. Therefore they are not real symmetries. So in what sense does it mean to spontaneously break a gauge symmetry? ian

imdoin an experiment with a strain gauge sensor to measure mass. the 2 strain gauges are in a wheatstone bridge and the wheatstone bridge is connected to 3 741 op amps to amplify the signal. i need an output of cetain voltages for certain masses input. My circuit is giving an output to high...

The propagator for gauge bosons in a spontaneously broken (non-abelian) gauge theory in the R_\xi gauge is (see Peskin and Schroeder eqn. 21.53) \tilde{D}^{\mu\nu}_F(k)^{ab}=\frac{-i}{k^2-M^{ab}}\left[g^{\mu\nu}-(1-\xi)\frac{k^\mu k^\nu}{k^2-\xi M^{ab}}\right]\,, where M^{ab} is the gauge...

how is general relativity cast as a gauge theory?

Hi: What's a gauge theory?, Is it just some kind of theory invariant with respect to some transformation? (like electrodynamics where the potentials are not sigle valued) and what is the importance of gauge theories in particle physics? Thanks

Please give me a defnition of the concept "synchronization gauge" I find in papers.

Quantization of Gauge theories ?? Hi , i am trying to learn the math formalism of Gauge Theories as far as i know they begin with the 1-form A= \sum_{i} T^{i}A_{\mu}^{i} where 'T_i ' are the generators of the Lie Group then we define the 2-form F= dA + (1/2)[A,A] and the...

Is it possible to describe spontaneous breaking of the local gauge symmetry in the standard Hamiltonian formalism, without any manual redefinition of the gauge field( A(r) -> A(r)+▽Λ(r) )? Detailed description of my question is given below.(Quite lengthy.. sorry.) 1. By the 'standard...

hello everyone! i've got a very special question on the gauge invariance (gauge group: SU(N), non-abelian) of the kinetic term in the lagrangian. is it invariant for any representation? i only know, that for the fundamental rep. this is true. to be more specific: the usual kinetic term...