Gauge Definition and 641 Threads

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...

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...

What is the definition of light-cone gauge? Is there any advantage for working in this gauge?

Hello, could someone help on this question?? ok, I'm trying to find out how much a piece of wood expands and contracts with changes in humidity and temperature, I'm sticking a strain gauge on the wood to detect the expansion and contraction of it. my question is if the temperature increase...

http://camoo.freeshell.org/25.8.pdf" Laura Latex source below. I won't be changing this if I edit the file, it's just for convenience if you want to grab latex code. n sec. 25.8, he says "recall the dual $^\ast F$ of the Maxwell tensor F. We could imagine a 'dual' U(1) gauge...

please see http://camoo.freeshell.org/dual_gauge.pdf" Thanks Laura

It occurred to me that I hadn't seen GR developed as a gauge theory in the same way QCD/electroweak are. Are there any technical obstacles, or is it reasonably straightforward? And if it is well known, can someone please point me to a reference? Thanks.

Need to do an experiment where I masure the strain of wood due to changes in temperature. I believe I need to use 2 strain gauges, one to measure the strain and the other to act as a dummy to cancel out any affects that heating will have on the strain gauge. I also know that a wheatstone bridge...

Local Gauge Symmetry ?? Trying to understand local gauge symmetry ================================ I have an undergraduate degree in physics, so I know basic quantum mechanics, but that's all. Still, I'm trying to understannd the concept of local gauge symmetry. I would appreciate if...

Hi i have just been given my physics coursework and wondered if anyone had any pointers or tips on how to answer? The question is on the expansion and contraction of wood with changes in temperature and humidity using a strain gauge. We have to explain how we would use lab equipment to...

I was looking at a derivation of the Landau levels in a crystal, and I had a question about the Landau gauge. The situation under consideration is a two dimensional system of non-interacting particles, exposed to a uniform magnetic field B directed along the z-axis (perpendicular to the plane of...

Hello, I'm currently doing a project that is concerned with the hopeful discovery of the Higgs Boson at LHC. I'll be running some code that my supervisor has produced, but before that he wanted me to understand more of the physics that is behind the Higgs mechanism. He has proposed a...

I do not see why it is not. I believe relativity is a gauge theory, due to the spin connection on a so(1,3) principal bundle. I have heard some people say it is not a gauge theory. Why do they say this, are they just stupid or what?

[SOLVED] invariance of maxwell's equations under Gauge transformation Homework Statement Show that the source-free Maxwell equations \partial_{\mu} F^{\mu\nu}=0 are left invariant under the local gauge transformation A_{\mu}(x^{\nu})\rightarrow...

This question comes from reading Schwarz' string theory book, which is why I put it in this section. But it seems like a general QFT question, so maybe this isn't the right forum for it. Starting with the sigma model action, reparametrization and Weyl invariance allow us to "gauge fix" the...

A village maintains a large tank with an open top, containing water for emergencies. The water can drain from the tank through a hose of diameter 6.15 cm. The hose ends with a nozzle of diameter 2.35 cm. A rubber stopper is inserted into the nozzle. The water level in the tank is kept 7.50 m...

Could anybody explain to me the difference between a Landau Gauge and Symmetric Gauge? I know the Landau Gauge is given by A = (0,Bx,0) producing a constant magnetic field in the z direction. I am *assuming* (process of elimination!) that A = ½B × r = (-yB/2,xB/2,0) is an example of a...

So I'm trying to read through Baez&Muniain's "Gauge Fields, Knots and Gravity". One thing I was particularly hoping to get out of this was a specific understanding of what a "holonomy group" is. In the relevant section (p. 231-233 in the version I'm looking at), Baez& describe a holonomy by...

Simple Gauge Pressure Question (a) Calculate the gauge pressure (it does not include atmosphereric P) required to compress pure water from 1.000 L to 989 mL. Give an answer in both N/m^2 and psi, lb/in^2. (b) What height in meters and feet of a 1x1 cm^2 steel bar (density=7.86 g/cm^3) is...

Hi all, I am having some issues understanding the design of the Bourdon Gauge, used to measure primary vacuum. Here is how we were told it works: http://xuneo.com/bourdon.png A tube is closed on one side, and linked to the vacuum enclosure on the other. When pressure drops, each...

Homework Statement The weight of your 1205 kg car is supported equally by its four tires, each inflated to a gauge pressure of 35.7 lb/in.^2. a) What is the area of contact each tire makes with the road? (in m^2) b) What gauge pressure is required to give an area of contact of 113 cm^2...

In an arbitrary number of spacetime dimensions, I am given a vector potential which is a function of all spacetime coordinates. How do I fix a suitable gauge in this case? The vector potential has same number of components as the number of spacetime dimensions. How do I check that after gauge...

For electromagnetic field we usually use the Lagrange's density -\frac{1}{4}F_{\mu\nu}F^{\mu\nu},\quad\quad\quad\quad\quad\quad\quad(1) but we could also use a simpler Lagrange's density -\frac{1}{2} (\partial_{\mu} A_{\nu})(\partial^{\mu} A^{\nu}),\quad\quad\quad\quad\quad(2) which...

what exactly constitutes a gauge transformation? is it a transformation using a differential operator?

I tried to convince myself it is Diff(M), but I failed. Most books say Bianchi Identities reduce the independent equations in Einstein's equations by 4, therefore there are some redundancies in the metric variables. As a result, there could be many solutions that correspond to one physical...

What does it mean to say to say that the electroweak interaction is described by a gauge field theory based on the SU(2)_{L}\timesU(1)_Y symmetry group? I know that SU(2) is a group of unitary matrices and U(1) is the circle group but I don't really see what the sentence means. I haven't taken...

I've been discussing some things with Samalkhaiat over in the conformal field theory tutorial. A part of that conversation (indicated by the new title) was drifting away from CFT matters, so we both thought it was better to move it into the Quantum Physics forum, to minimize pollution of the...

I was wonder why some textbooks define it as D_u=d_u-ieA_u and other textbooks define it as D_u=d_u+ieA_u. I am not clear whether this choice doesn't matter or is one notation correct.

Homework Statement Water flows steadily from an open tank. The elevation of point 1 is 10.0 m, and the elevation of points 2 and 3 is 2.00 m. The cross-sectional area at point 2 is 0.0480 m^2; at point 3 it is 0.0160 m^2. The area of the tank is very large compared with the cross-sectional...

GR as a Gauge theory ?? don't know if this is true or not, but i have been reading books by ROvelli (LQG) or 'Gauge theories' the question is could we study Gravity as the set of functions A_{\mu}^{I}(x) Then we write the Einstein Lagrangian (or similar) as: \mathcal L =...

Marcus! Surely, I’m not the only one reading the links that you provide! http://arxiv.org/PS_cache/arxiv/pdf/0706/0706.1534v1.pdf Coupling gauge theory to spinfoam 3d quantum gravity Simone Speziale June 11, 2007 Note: The Acknowledgments: The author is particularly grateful to Carlo...

I have been told that using a metric g_{00} = -a^2(\eta)(1+2\psi) g_{oi} = g_{i0} = a^2(\eta)\omega_i g_{ij} = a^2(\eta) \left[(1+2\phi)\gamma_{ij} + 2\chi_{ij} \right] and a gauge transformation x^{\bar{\mu}} = x^{\mu} + \xi^{\mu} with \xi^0 = \alpha \xi^i = \beta^j gives...

Ok, I have a question about this Fade'ev Popov procedure of teasing out the ghosts when one quantizes a non-Abelian gauge theory with path integrals. The factor of 1 that people insert, for some gauge fixing function f, and some non-Abelian symmetry \mathcal{G} is: 1=\int \mathcal{D}U...

1. For a project on elementary particle physics I have to consider a gauge theory with the gauge group SU(5) coupled to a scalar field. I am to use a certain non-zero vacuum expectation value for the scalar field and check what happens to the gauge bosons. I have already done this for...

How would one know in general, whether an original gauge symmetry in the theory is still gauge symmetrical after symmetry breaking? I mean is there a theorem or something like that? And the other way around, is there a general way of knowing whether there is the possibility of a hidden, i.e...

Many seem to argue it is but Steven Weinstein argues in his paper http://philsci-archive.pitt.edu/archive/00000834/00/gr_gauge.pdf" it is not. He argues that the diffeomorphism invariance of GR is more restrictive than gauge invariance since in the case of diffeomorphism invariance the...

Homework Statement Cylindrical tank of water is 20m tall, and full. atmospheric pressure is 1.01x10^5 Pa and the density of water is 1000Kg/m^3. Find absolute pressure 6m above the bottom. Homework Equations P=P*sub*a + pgh The Attempt at a Solution I got so far... P=(1.01 x...