Gauge Definition and 685 Threads

If I have a theory... some Lagrangian and I need to impose a gauge condition... what is more preferable 1) The subject gauge naturally arises from the structure/type of the lagnagian (Like a Lorentz gauge that can automaticaly arise in Electrodynamics) 2) Or I have just to impose it...

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...

Dear all, I'm reading Polchinski's text of string theory. In section 1.3, he demonstrates how to quantize the free point particle in the light-cone gauge. I'm confused with a step in the follows. Begin with the action, S = \frac{1}{2}\int d\tau\left(\eta^{-1}\dot{X}^\mu\dot{X}_\mu -...

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...

Can somebody explain the parities of photons, W, Z and gluons? QFT says that bosons and antibosons have the same P parity. But the P parity of the gauge bosons is rarely given. Sometimes photons are said to have negative parity, while other say this is only the case for electric dipole...

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...

Help With Portable Weigh Station Using Strain Gauge Allright I'm a freshman in college and we have a project due for this semester. The task was to create a weigh station using a strain gauge to measure anything from 2,500lbs cars to 96,000lbs semi-trucks, while giving 100lbs for error...

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...

The gauge pressure in each of the four tires of an automobile is 240 kPa. If each tire has a "footprint" of 220 cm2, estimate the mass of the car. @Mods: please move if this is too easy for this forum.

Why is local gauge invariance needed in qft? I read that is allows interactions whereas global gauge invariance does not but was given no reason.

Hi folks! Another stupid question: Consider a Yukawa coupling \lambda \bar{\psi}_1 \psi_2 \phi where \phi is a scalar field in the (2,-\frac{1}{2}) representation and \psi_1 and \psi_2 are lh. Weyl fields in the (2,-\frac{1}{2}) and (1,1) representation of \mathrm{SU}(2) \times \mathrm{U}(1)...

Homework Statement b) A spherical balloon is inflated to a diameter of 60.0 cm. Assuming that the gas in the balloon is of atmospheric pressure (101.3 kPa) and is at a temperature of 20.0 oC. The above balloon is then taken by a diver 25.0 m under the sea. The temperature of the seawater...

At page 52 of 4th chapter in "An Introduction to gauge theories & modern particle physics" by Leader & Predazzi one can find such statement: "We must therefore rearrange (4.2.4) so that we can identify the field that multiplies\frac{1}{2}\left(1+\tau_{3}\right) as gauge boson that remains...

Forces are mediated by gauge bosons. If, for instance, you look at a collision between 2 electrons, is there a definite/calculable number of photons exchanged? Do they have a particular frequency? Do we expect the same thing of gravitons? Does that mean the action of forces is quantized...

We use, among others, Penning pressure gauges for determining pressures (aprox. 1E-7 to 1 mbar (about the same in Torr... for the Americans here ;-) ). The Penning is placed just outside the recipient, behind a valve to make sure its never in pressures of 1mbar or more. When using a smaller...

Homework Statement The general gauge transformation in electrodynamics is {\bf A}' = {\bf A} + \nabla \lambda and \phi ' = \phi - {{\partial \lambda}\over{\partial t}}. In the Lorentz gauge, we set \nabla . {\bf A} + {{\partial \phi}\over{\partial t}} = 0 . My question is: Is the...

What are gauge theories? Any simple explanations? Why are they so important? Whats renomalization?

I'm an undergraduate in physics, I'm on my 2nd year. I have to write this assignment about the Higgs particle and gauge theory. There are quite some things that are unclear to me however. Since I'm only on my second year I don't know a lot of deep math like group theory, just basic stuff. I know...

As far as I understand, the gauge group for Ashtekar variable theory for General Relativitiy is SU(2), because its group is three- dimensional. But, why is this SU(2) instead of SO(3)? Are there any plausible reasonings behind this? And, are there any phenomenological differences if the gauge...

Dear All, I'd be grateful for a bit of help with the following problems: Consider the Lagrangian: \displaystyle \mathcal{L} = (\partial_{\mu} \phi) (\partial^{\mu} \phi^{\dagger}) - m^2 \phi^{\dagger} \phi where \phi = \phi(x^{\mu}) Now making a U(1) gauge transformation...

I am an Italian physicist working in the field of condensed matter and non-relativistic quantum mechanics. Unfortunately my background in general relativity is very poor. In the last few monthes, as a hobby I am trying to learn a little bit of general relativity. Besides reading textbooks on...

I have an assignment in which I have to design a laboratory experiment (not real, only in theory i.e. planning) to investigate how the resistance of a strain gauge attached to a piece of wood varies with the temperature of the wood. *IMPORTANT* My teacher said keep it simple, do not over...

Could anybody help me please? :cry If I have quarter- bridge strain gauge circuit, where strain gauge will have its initial resistance and i will add another 3 resistors, 1 on the same side like strain gauge, and another 2 on the opposite side, so I will balance circuit and my voltmeter...

Hi! Im measuring how much wood expands in different temperatures using a strain gauge. do i need to use a wheatstone bridge circuit schematic? or else how do i heat up the wood without spoiling the strain gauge. Actually how will i heat up the wood anyway? Also how would i draw a diagram to...