Gauge Definition and 641 Threads

I've looked everywhere and I haven't found an explanation of why is it useful to introduce gauge conditions. I've also searched in this forum, and none of the existing threads I've read answered my question. I apologize if there is and I have failed to find it. My problem is that, as I see it...

Homework Statement objects A and b are submerged at a depth of 1m in a liquid with a specific gravity of 0.877. Given that the density of object B is one third that of Object A and that the gauge pressure of object A is 3atm, what is the gauge pressure of object B? assume atmospheric pressure...

Homework Statement For a gauge function G(t,q) where , does or have any alternative form or can they be expressed in any other way? Homework EquationsThe Attempt at a Solution

Well, I'm planning to learn from this book when i finish Shankar's Principles of Quantum Mechanics, if it fulfills the requiriments in this part, but from where i can learn the Special Relativity necessary to tackle this book?

Homework Statement A barrel contains a 0.110 m layer of oil and a density of 690 kg/m3 floating on water that is 0.300 m deep. What is the pressure at the bottom of the barrel? Homework EquationsThe Attempt at a Solution Poil + Pwater = Ptotal My question is why am I using this formula? I...

Hey I've built a speaker and the cone is about 20cm in diameter. I need help choosing the wire gauge for the voice coil though. When I look at this chart http://www.powerstream.com/Wire_Size.htm I can't really see anything that will work. My stereo puts out 50W and if I want the resistance to be...

Homework Statement We wish to make a precipitation meter shaped like a paraboloid ##z = x^2 + y^2, 0 \leq z \leq 10##. Devise a scale on the z-axis that tells you the amount of precipitation in cm. In other words, at what height ##z = h## is the surface of water in the dish when there has been...

Due to its form, gauge transformations for the typical electrodynamics potentials are "local" in nature. That`s: they exists for path connected topological spaces. So, there exists global gauge transformations or are all of them local in nature?. If the answer is "yes", i.e. if there are global...

I am trying to derive the potential based Lorentz gauge, but I am not sure if I am on the right track. Why the second partial derivative of vector potential must be 0? Please correct me where I got this wrong.

Hello everyone, I have been reading around that when performing the analytic continuation to Euclidean space (t\to-i\tau) one also has to continue the gauge field (A_t\to iA_4) in order to keep the gauge group compact. I already knew that the gauge field had to be continued as well but I didn't...

Homework Statement A person has a 5200 N/m^2 gauge pressure in a 0.01m radius artery, with blood flowing at 0.5 m/s. the gauge pressure outside the artery is 3200 N/m^2. When using her stethoscope, a physician hears a fluttering sound farther along the artery. the sound is a sign that the...

Hi, I am a little confused of derivation of Coulomb Gauage. (2) First, prime notation is adopted to describe the magnetic field density source current. Non-prime notation is for position that we are specifically interested in (ex. the position magnetic force acts on)...

A complex classical field Φ of particles is, by itself, invariant under global phase changes but not under local phase changes. It is made gauge invariant by coupling it with the EM potential, A, by substituting the covariant derivative for the normal partial derivative in the Lagrangian. But...

Spinors in $N=2, D=4$ supergravity can be simplified using gauge transformation and thus canonical spinors can be found. In the case of $N=2, D=4$ supergravity the gauge transformation Spin (3,1) is used. My question is how do we know which transformation can be used in a certain theory in order...

Hello. I'm trying to wrap my head around how Lagrangians work in classical field theory. I have a book that is talking about the gauge invariance of the Lagrangian: \mathscr{L} = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu}-J^\mu A_\mu. It shows that we can replace A^\mu with A^\mu+\partial^\mu\chi for...

Homework Statement Define n=(x + iy)/(2)½L and ñ=(x - iy)/(2)½L. Also, ∂n = L(∂x - i ∂y)/(2)½ and ∂ñ = L(∂x + i ∂y)/(2)½. with ∂n=∂/∂n, ∂x=∂/∂x, ∂y=∂/∂y, and L being the magnetic length. a=(1/2)ñ+∂n and a†=(1/2)n -∂ñ a and a† are the lowering and raising operators of quantum mechanics. Show...

A symmetry of a physical system is a physical or mathematical feature of the system that is preserved or remains unchanged under some transformation. For example, the speed of light is an example of symmetry and its value will always will always remain the same no matter where and what...

The part I understand: I understand that the spontaneous symmetry breaking of the Higgs produces the 'Mexican hat' potential, with two non-zero stable equilibria. I understand that as the Higgs is a complex field, there exists a phase component of the field. Under gauge transformations of...

I asked this question to PhysicsStackExchange too but to no avail so far. I'm trying to understand the way that the Higgs Mechanism is applied in the context of a U(1) symmetry breaking scenario, meaning that I have a Higgs complex field \phi=e^{i\xi}\frac{\left(\rho+v\right)}{\sqrt{2}} and...

Is there a physical reason why all gauge groups considered in SM and especially beyond are always semisimple? [+ U(1)] What would happen if they were solvable?

I've heard the claim that the gauge freedom of the general Lagrangian can be used to derive the Lorentz force on a charged particle. I understand that Langrangian gauge freedom allows A⋅v -∇φ to be unaffected by the gauge freedom in defining the EM potentials, but this seems like a convenient...

From what I have read: Gauge Pressure: The amount by which the pressure measured in a fluid exceeds that of the atmosphere. and Absolute pressure: Total pressure at a point in a fluid equaling the sum of the gauge and the atmospheric pressures.So Absolute pressure= Patm+ P-Patm= P (Which is...

Hi! I'm in a situation with threads that are being torqued, and unthreaded, and then torqued again hundreds of times per day. While torqued they are required to lift thousands of pounds of load. We've experienced failures where the threads appear to have worn/galled to the point that they...

Homework Statement Homework Equations The Attempt at a Solution I'm trying to find the principal strain, then from that find stress. The poisons ratio should be around 0.3 for this experiment. My result is about 100 micro strain higher than what my class mates got. Can anyone see...

Homework Statement Objects A and B are submerged at depth of 1m in a liquid with specific gravity of 0.877. Given that density of object B is one third that of object A and that the gauge pressure of object A is 3atm, what is the gauge pressure of object B? (assume atmos pres is 1 atm and that...

Can there be interactions that are symmetric under low temperatures but exhibit spontaneous symmetry breaking under extremely low temperatures? (Maybe that symmetry breaking temperature is so low that it couldn't be discovered in experiments) Does electromagnetism split into electricity and...

I've having trouble understanding one of the consequences of using the length gauge. The length gauge is obtained by the gauge transformation ##\mathbf{A} \rightarrow \mathbf{A} + \nabla \chi## with ##\chi = - \mathbf{r} \cdot \mathbf{A}##. Starting from the Coulomb gauge, we have $$...

please explain what gauge symmetry is, gauge transformation is, gauge invariance is, and also how gauge invariance deletes the timelike polarization of a massless vector boson. without fancy math and formulas.

Urs Schreiber submitted a new PF Insights post Examples of Prequantum Field Theories II: Higher Gauge Fields Continue reading the Original PF Insights Post.

Although I have a good understanding of how to do calculations in gauge field theory, I am still dissatisfied with my understanding of why we use them in the first place. From a philosophical point, it should be possible to characterize a gauge theory in terms of observables only. I suppose one...

Urs Schreiber submitted a new PF Insights post Examples of Prequantum Field Theories I: Gauge Fields Continue reading the Original PF Insights Post.

If a theory is gauge invariant and one chooses to fix a particular gauge, having done this is it then possible to make a gauge transformation from this chosen gauge to another gauge, or have we already "spent" the gauge symmetry? Apologies if this is a really basic question, but I've got myself...

Is anyone able to explain in basic terms a thick EE student could understand, the significance and a bit about what Guage Fixing, or maybe gauge theory in general is? (or especially for FE simulation) making heads or tails of https://en.wikipedia.org/wiki/Gauge_fixing is not easy. A nice simple...

Buried in a recent talk by John Ellis, the following passage: Reference 92 is Weinberg & Witten 1980, reference 93 is a talk by Zohar Komargodski at the same meeting.

<<Mentor note: Moved from other thread.>> I have 4 questions: 1. Why Weinberg angle affects neutral boson mixing, while W+ and W- are unaffected? 2. Is there any relation between Weinberg angle and CP violation angle? Are they absolutely independent? 3. How our world would be different if...

From a recent thread: Is this true of gluons? Doesn't the color charge invert under CPT? (For example, a red-antigreen gluon's antiparticle would be a green-antired antigluon.)

So, I am following the PI lecture series by Neil Turok. He starts with the following description of harmonic gauge condition $$g^{\mu \nu}\Gamma^{\lambda}_{\mu \nu}=0$$ He then claims that for linearized gravity (weak field) i.e. $$g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu} $$ with $$ |h_{\mu...

If I have a theory withsome gauge symmetry, I don't understand why we want to fix a gauge. It seems to me to be 1. artificial 2. ignoring a real symmetry of the equations For example in electromagnetism, we can use the lorentz gauge, but why would I? It removes a degree of freedom that should...

hi~I am a beginner of Gauge theories,and I have some questions~ Why we need loacal phase invariance? Because i cannot understand why we assume phase depend on the position.Is there any theory leading to this asssumption?

Homework Statement Water flows at 0.25 L/s through a 9.0-m-long garden hose 2.0 cm in diameter that is lying flat on the ground. The temperature of the water is 20 ∘C. What is the gauge pressure of the water where it enters the hose? Side question: does the velocity of the water flow need to...

I have questions regarding the 24 gauge bosons of the SU(5) model. I keep seeing this matrix popping up in the documents I'm reading with no real explanation of why: First of all I'm wondering how this is constructed, which means I'm wondering what the V_{\mu}^{a} look like (I already have...

Hi! One of our professors told us once that in solving problems, always use absolute pressure in the computations. Then one time, I was solving some problems from Dr. Felder's Principles of Chemical Processes book, I often noticed that the pressures used in computations were not always in...

I know that we have a free parameter in the relativistic potential for electromagnetism. I also know that we can introduce this as a scalar field ψ which gives this free parameter. I understand that this can be related to U(1) by mapping ψ: ---> e^iψ, which is the U(1) group. It just seems a...

By fixing a gauge (thus breaking orspending the gauge symmetry), the model becomes something easier to analyse mathematically, such as a system of partial differential equations (in classical gauge theories) or a perturbative quantum field theory (in quantum gauge theories), though the...

I want to understand the 'vertex factor' of 3-bosons field and 4-bosons field but get confused. (I know the lagrangian and have computed the interaction vertices already) only need to understand the vertex factor. In other words, I want to learn how 3-boson vertex and 4-boson vertex are...

When we start by postulating local SU(2) gauge invariance for our weak isospin doublets \begin{align} \psi &= \begin{pmatrix} \nu_{e} \\ e^{-} \end{pmatrix}_{L} \end{align} etc., we have to introduce massless gauge fields to preserve the Lagrangian's invariance. For SU(2) this demands 3...

I hope someone with a deep conceptual understanding of terminologies would help me out here. I am having starting problems in understanding the approach of gauge theories. I have read suggested threads and I am still at a loss. I am an experimental physicist and know basics of electrodynamics...

Electromagnetism: Multivalued potential voltage? It's been my understanding that specifying the electric and magnetic potential at all points in a system determines the electric and magnetic fields--and more, that we can fix a particular gauge, and it all still works. Perhaps I've been naive...

Homework Statement Homework Equations Please see below. The Attempt at a Solution No idea about part (a). Trying to work out part (b), I asked my tutor and he said: I think it's this. We have the Dirac Equation $$\left ( i \hbar \gamma ^{\mu } \partial_{\mu }-mc\right )\Psi =0$$ but for a...

I recently learned that with (local) gauge invariance, functional quantization needs to factor out volume factor(Faddeev-Popov procedure). Why does this has to be done?Just to remove infinity? As far as I am concerned, ##\phi^4## theory contains invariance(for example ##\phi\to\phi\cdot e^{i...