Gauge Definition and 685 Threads

After the first explanation of superconductivity by Bardeen, Cooper and Schrieffer, it was for several years a matter of concern to render the theory charge conserving and gauge invariant. I have been reading the article by Y. Nambu, Phys. Rev. Vol. 117, p. 648 (1960) who uses Ward identities to...

Hello all quantum nerds! :D I have a question regarding the "classical" limit of quantum fields, and in particular gauge fields. When we for instance do a surface integration in QFT, we let phi -> 0 as V->oo why? this is said in textbooks to correspond to the "classical limit", and...

Im reading "A first course in String Theory" by Zwiebach and it says that when applying a gauge parametrization in the form of n_\mu X^\mu = \lambda \tau we can take the vector n_\mu so that for open strings connected to branes (fixed end points), n^\mu \mathcal{P}^\tau _\mu is conserved...

http://arxiv.org/abs/1004.4866 Unification of gravity, gauge fields, and Higgs bosons A. Garrett Lisi, Lee Smolin, Simone Speziale (Submitted on 27 Apr 2010) We consider a diffeomorphism invariant theory of a gauge field valued in a Lie algebra that breaks spontaneously to the direct sum...

Hello folks. I have a sangamo weston temperature gauge. Back of this gauge there is 2 screws and a small wire(5cm) connecting the 2 wires. I want to taking measurement in 1m distance from the gauge so I tried to replace this wire with a copper one but the gauge doesn't work with copper wire. I...

Homework Statement Introduce a TT coordinate system in which, at time t=0, the two particles are both at rest. Use the geodesic equation to show that subsequently they both always remain at rest in the TT coordinates, despite the action of the wave. This means that the vontravariant...

Hello, I have read an interesting paper from the Proceedings of the American Philosophical Society about the use of the V-2 rocket at White Sands, New Mexico for high-altitude research. In it the different gauges for atmospheric pressure measurement were mentioned, as well as the difficulty to...

Hi all, I've been studying the path-integral quantisation of gauge theories in Zee III.4. My understanding is roughly as follows: that one can think of the differential operator in the quadratic tems in the lagrangian as a linear operator between infinite dimensional spaces (morally...

Hello, suppose you start with Yang Mills theory with some gauge group G, for example SU(5). Then you turn on a gauge bundle, say a U(1) bundle, and the group breaks down. I know that from hearsay but I wonder how would you describe that explicitly in formulas? meha

http://arxiv.org/abs/1004.0693 Gravity as the Square of Gauge Theory Zvi Bern, Tristan Dennen, Yu-tin Huang, Michael Kiermaier (Submitted on 5 Apr 2010) We explore consequences of the recently discovered duality between color and kinematics, which states that kinematic numerators in a...

Suppose I have a gauge potential A_{\mu\nu}, which is totally antisymmetric, if, say, the theory is in 6 dimensions, so that there are 6\times5/2 = 15 degrees of freedom. For the action S = \int d^6x F_{\mu\nu\rho}F^{\mu\nu\rho} , where F_{\mu\nu\rho}\equiv \partial_\mu A_{\nu\rho} +...

Homework Statement Take the Schrodinger equation for a point particle in a field: i\hbar \frac{\partial \Psi}{\partial t} = \frac{1}{2m}(-i\hbar\nabla - q\vec{A})^2\Psi + q\phi\Psi I'm supposed to determine what the transformation for Psi is that corresponds to the gauge transformation...

Suppose I have a manifold. I say that it can support a certain configuration of gravity field described by metric tensor \gamma. I do not write \gamma_{\mu\nu}, because that would immediately imply a reference to a particular chart. A tensor field, however, exists on a manifold unrelated to this...

Homework Statement I want to derive Gauge symmetries of the following gauge theory: S=\int\;dt L=\int d^4 x \;\epsilon^{\mu\nu\rho\sigma} B_{\mu\nu\;IJ} F_{\mu\nu}^{\;\;IJ} Where B is an antisymmetric tensor of rank two and F is the curvature of a connection A i.e: F=dA+A\wedge A...

Homework Statement The weight of a 1142-kg car is supported equally by the four tires, which are inflated to the same gauge pressure. What gauge pressure is required so the area of contact of each tire with the road is 96.5 cm^2? W = 1142 kg A = 96.5 cm^2 Homework Equations No idea...

Homework Statement I recently did a bending lab with a WB Strain Gauge in a bunch of different configurations. One measurement in particular is bothering me. Referring to the figure below, there are four strain gauges, Yellow, Orange, Black and Red mounted to a cantilevered beam with an...

Hello i am trying to convert the strain gauge readings i took in a lab from an I beam that was subjected to torsion. I am trying to convert the microstrain readings to stress and shear stress. I have the following information the Yield strength of the I beam and the youngs modulus but not the...

Homework Statement Water flows through a .259m radius pipe at the rate of .125m^3/s. The pressure in the pipe is atmospheric. The pipe slants downhill and feeds into a second pipe with a radius of .190m, positioned .796m lower. What is the gauge pressure in the lower pipe? The acceleration of...

http://golem.ph.utexas.edu/category/2010/03/an_invitation_to_higher_gauge.html#c032039

Ok, so what I am looking for, as the title suggests, is a strain gauge data acquisition board. Currently, we have been using all sorts of National Instruments stuff to obtain our goals. To this point they have worked fine, but now we need to seriously downsize for a new lab device we are...

Hi there! Few weeks ago I came upon the following problem: Let B be a vector field derivable from a vector potential A (on a simply connected topological space, smooth enough and everything well established so that mathematicians do not have to care about), i.e. \vec B=rot \vec...

Homework Statement So I was doing a problem out of Merzbacher 3rd edition (end of chapter 4 problem 3); the homework set has already been turned in but I wanted to run this by you all and see what you thought. I am essentially working with a particle in a 1-d ring constrained to the x-y plane...

Consider a one dimensional gauge theory where the field has mass. The term, m^{2}A^{\mu}A_{\mu} is the conventional mass term. What if you find terms in your Unified Field Theory lagrangian of the form M_{\mu\nu}A^{\mu}A^{\nu} ? In this case M_{\mu\nu} is constant. When it is...

Can someone please help me out with mass terms in the general case for a lagrangian? It is known that for n scalar fields, any quadratic in these fields will be a mass term. For classical fields \varphi_{j} with the most general possible expression being M^{jk}\varphi_{j}\varphi_{k} , the...

Homework Statement Show that it is always possible to pick a gauge so V' = 0. Homework Equations We weren't given any, but I've been working with: (a)\vec{E} + \frac{\partial\vec{A}}{\partial{t}} = -\nabla{V} (b)\vec{A'} = \vec{A} + \nabla{\psi} (where \psi is a scalar function) (c)V' =...

Hi... Would you please advise me what does gauge fixing term do (physical point of view) ? Does it eliminate unnecessary spin components from lagrangian for example: Vector particle has two (massless case) or three (massive case) degrees of freedom. Vector itself has four, and a vector...

just some dilemma I ran into I have an experimental setup with a pressure transducer output connections (wires)...I deemed now that a pressure gauge alone will suffice. How do I connect the wires to a pressure gauge? Or do I need to re-do everything?

hi, Zee in QFT in nut shell says "The most unsatisfying feature of field theory is the present formulation of gauge theories. Gauge symmetry does not relate 2 different physical states but the same physical state. We have this strange language with redundancy which we cannot live without" He...

What is meant by the term "gauge singlet"? Can anybody please explain what is meant by the term "gauge singlet"? To be more specific, I got the term in a discussion on wess-zumino lagrangian where the superpotential contains the term:a_i \phi_i . The author claims that in order the theory to...

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...

Hi, I have a question on the gauge formulation of gravity and supergravity. The question that I have first concerns the gauge formulation of gravity. As I understood from various articles by Sardanashvily (see e.g. D.Ivanenko, G.Sardanashvily, The gauge treatment of gravity, Physics Reports...

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"? Are "coordinate system" and "gauge" the same thing? What about "coordinate transformation" and "gauge transformation"?