Fields Definition and 1000 Threads

This is more of a QFT question, so the moderator may want to move it to another forum. The simplest example of a QFT that I learned was the scalar field; in Sakurai's 1967 textbook. I know the Higgs is a J=0 particle. Is it described by the simple scalar field discussed in Sakurai's text? I ask...

Homework Statement four point charges are placed at the corners of a square as shown in the figure having side 10 cm.If q is 1μC then what will be electric field intensity at the centre of the square? Homework Equations 3. The Attempt at a Solution [/B] Half of diagonal a/√2 0.1/√2...

I have no idea how lethal/strong space radiation is, but i do have an idea that most of it is from the sun perhaps? I also know that the prime factor to deflect this radiation is magnetic field and the ozone layer. I think the magnetic field handles only particle radiation and atmosphere handles...

¿How is possible deduce the Lagrangian of the fields of a theory knowing only his Feynman Diagrams?

I need help explaining that this assumption is not correct or correct: A product uses Radio waves to turn on a LED. Radio waves can be a form of electromagnetic fields therefore, a Hall Effect sensor could be used in this device to turn on that LED.

My professor in Classical Electrodynamics is great and all, but sometimes he has trouble understanding what it is that I don't understand. So here I am. Let's say we have the some sort of (monochromatic) radiating system generating a electric field with Fourier amplitude Eω(x) and want to...

As fields ##\phi ## are ill defined at precise time and position i read that fields have to be smeared. So we have test functions f in bounded regions in space time. We have a Hilbert space and ##\phi (f) ## is an operator which acts on H. Maybe we can retrieved the usual wave function when it...

Homework Statement A satellite is designed to orbit Earth at an altitude above its surface that will place it in a gravitational field with a strength of 4.5 N/kg. a) Calculate the distance above the surface of Earth at which the satellite must orbit b) Assuming the orbit is circular...

Most threads discussing this subject have only confused me further, gone offtopic and later been locked. I have a basic yes/no question, which is the following: is there one single electromagnetic field in the universe that is excited locally (creating fields, in apparent plural, although...

Homework Statement I was just studying the Klein Gordon equation with fields. In particular I was reviewing the continuity equation. In the derivation for it, the usual approach is to take the klein-gordon equation (I'm using 4-vector covariant notation), multuply by the complex conjugate of...

Does anyone know if they have considered using ultra high efficiency magnets to create an oscillating pulse into the energy of the electron orbital shells? This may in turn break the Coulomb barrier.

I've read that matter and energy fields occupy all of space, and that space is integral with time, so I'm wondering whether it might be consistent with contemporary physics for undetectably small proportions of the mass of matter and / or energy to occupy arbitrarily large proportions of an...

Homework Statement Explain the circumstances that enable a particle to move un-deflected with uniform motion through an electric field if it is given an initial velocity perpendicular to the electric field. Assume the electric field is the only field present.[/B] Homework EquationsThe Attempt...

Hi all! I am a 13-year-old that is very interested in physics. I am currently studying fields, and I have gotten into some advanced parts of field theory. With that, I have 3 big questions: 1. In vector and higher order tensor fields, what does it mean to "observe the field from point...

How does an electric charge produce an electric field? How is this field maintained over time without the input of energy? When the charge moves, why is or isn't there any remnant of the field left behind in space?

Homework Statement 1) Describe and explain what happens to the electron beam on the screen of a teltron tube as the EHT(electrical high tension) voltage increases from 3000V to 3500V. 2)What is the effect of E field on light waves? Homework EquationsThe Attempt at a Solution 1) The beam...

Homework Statement In a book I find the following derivation: \int (J \cdot \nabla ) \frac{\bf{r} - \bf{r}'}{|\bf{r} - \bf{r}'|^3} d^3\mathbf{r'}= -\sum_{i=1}^3 \int J_i \frac{\partial}{\partial r_i'} \frac{\bf{r} - \bf{r}'}{|\bf{r} - \bf{r}'|^3} d^3\mathbf{r'} \\ = -\sum_{i=1}^3 \int J_i...

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm? I have used the formula...

Hello, I am in a calc 1 general physics 2 summer session class and missed the lectures on this due to sickness. I'm really confused on applying coulomb's and gauss's laws to find the electrical field of a sphere or outside a sphere. This is of both variable and constant charge densities. I've...

Can someone correct my understanding on electromagnetic waves please; I've clearly got the wrong end of a stick somewhere, but can't figure out where my misunderstanding is! Thanks. If I draw a classic EM wave with the electric field on the up and down axis and the magnetic field at right...

Homework Statement A ring with radius R has a constant current and is rotating around a diameter with constant angular velocity omega. 1)Calculate the radiation fields far from the ring. 2)What's the direction of the polarization for an observer along the axis of rotation? 3)What are the...

I'm just trying to think of a qualititive solution to the following thought experiment: I have an RF source of very large voltage driving a signal towards point A (say, a capacitor or a dipole antenna). The source itself is not really part of this experiment, but I just want a sinusoidal...

What is the interaction Lagrangian of matter and graviton fields?So(on the answer)we can say about the nonrenormalization.Why is the divergence of two gravitons diagram able to be the limit of the coincidence of the verties.So we can say about the nonrenormalization.

Please forgive me if I am posting in the wrong forum. Also the board limits the length of the title. I wanted to ask about Effect of high intensity electric and magnetic fields on spacetime. To begin, 15 years ago this was published...

Please forgive me if I am posting in the wrong forum. Also the board limits the length of the title. I wanted to ask about Effect of high intensity electric and magnetic fields on gravity. To begin, 15 years ago this was published...

**Not a homework question. In my professor note, it says that: "If a material causes magnetic field (in parallel direction to the surface charge) below a boundary is not the same as the boundary (in parallel direction to the surface charge) above the boundary, then a surface current is...

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...

I'm trying to work up some examples to help me understand this concept. Would the periodic flow on a solid torus be transverse to it's boundary?

I have a question that I can't figure out , there is a toroidal transformer , and the core has an attached part on which another coil is wound. the main coil of the toroidal transformer is connected to a DC source. which creates a static magnetic field in the torus core. the other coil at the...

It could be that I'm misinformed, but I heard electrons at rest have magnetic fields. I thought that magnetic fields required a charge to be traveling at velocity before a magnetic field would arise. If this is the case could someone help me out? If an electron has a magnetic field at rest what...

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...

Since Mars doesn't have a magnetic field of its own due to the cooling of it's core, what if you took a strong magnet from Earth say a superconductive magnet or electromagnet, will the small magnetic field (relative to mars) repel solar radiation, solar flares and other background radiation form...

This started with me trying to read up how static electric/magnetic fields are described with photons, but it quickly evolved into the realization that I don't really know how the photonic viewpoint describes *any* changing EM field that isn't a neat monochromatic wave. Some sites mention...

Homework Statement Two positive charges +Q are affixed rigidly to the x-axis, one at x = +d and the other at x = -d. A third charge +q of mass m, which is constrained to move only along the x-axis, is displaced from the origin by a small distance s << d and then released from rest. (a) Show...

"a +4nC charge is 6/0 cm along a horizontal line toward the right of a -3nC charged object. Determine the E field at a point 4.0 cm to the left of the negative charge." From what I understand, it goes Point ___ 4cm ____ (-3nC) _____ 6cm ____ (+4nC) Using that, I got the answer to be -14.75 nC...

Homework Statement I am going through the book "Symmetries in Fundamental Physics" by Kurt Sundermeyer and in his part on deriving Yang-Mills theories from a Kaluza-Klein perspective I seem to be stuck on a small step in the derivation. Homework Equations He expands the metric in a typical...

It's easy to find references which explain that the photon is the force carrying particle for the electromagnetic force (ie https://en.wikipedia.org/wiki/Force_carrier). Similarly there are force carrying particles for other forces, like W and Z bosons carry the weak force. This has always...

I know this question has been beaten to death, but I haven't seen a response that clearly (to me) answers the following: 1. Magnetic fields *can do work* on intrinsic dipoles, right? (e.g. two electrons can do work on one another via their intrinsic spin). 2. Magnetic materials can do work on...

if there is an uniform, infinitly extended,magnetic field that is changing with a law B(t), I can calculte the induced electric field using an arbitrary circle; then the induced circuitation on the circle is \epsilon _i=-\pi r^2 \frac{dB(t)}{dt} , and since the symmetry of the system ( infact...

Does QM contain both discrete particles and fields? If so, why aren't these two mutually exclusive? It seems like one is chunky and the other continuous.

Homework Statement 560 nm light is collimated and passes as a parallel beam in a direction perpendicular to the ##x+y+z=0## plane. It is polarized parallel to the ##(y-z)## plane. Treating it as a plane wave, what are the real E and B fields? Intensity of the beam is ##1 \ mW/cm^2##. Make...

Homework Statement This isn't necessarily a problem, but a question I have about a certain step taken in showing that the electric and magnetic fields are transverse. In Jackson, Griffiths, and my professor's written notes, each claims the following. Considering plane wave solutions of the...

Hi guys, I was tutoring some students and I was explaining them how to calculate the capacitance between two parallels planes. They made me some questions and actually I am not quite sure about my answers! I started by showing them how to calculate the electric field generated by a single...

For the Godel metric (in Cartesian coordinates), I derived the Einstein tensor Gμν as well as its inverse Gμν in a coordinate basis. I tried converting the inverse into an orthonormal basis using a technique for this that was taught to me on another thread long ago. When I tried using said...

Hi everyone. I have written similar threads about this in the past, but I thought that now would be a good time to revive this topic (as a snapshot of STEM demand, if you will). So I would like to ask the following questions: 1. Which STEM fields are actually in demand in the US as of 2015? 2...

Homework Statement Assume that I = 5.0A. What is the magnetic field at point b in the figure? Give your answer as a vector. Homework Equations Ampere's Law - B = (μ0I)/(2πr) The Attempt at a Solution I tried plugging the given numbers into Ampere's Law for point b, which gave me B =...

Problem I have a project for my university class on the Higgs fields and how it impacts the standard model, and how the Higgs particle is formed and decays into particles with the probability of decay based on the mass of the particles it will decay into. I need resources that I can cite like...

Homework Statement Reading a journal from that crazy old retired physics professor on the hill, you stumble upon a scheme to generate high frequency (HF) radio waves (λ = 10 m). It requires generating an electric field that diverges from a point and increases in strength linearly with respect...

I am a third year undergraduate physics major. Often time people ask what I want to do with physics, and I didn't really have an answer for them. I guess I always assumed I'd pursue a masters degree in some kind of engineering, but I want to be able to do something that I'm passionate about...

Hi I am doing some exam revision for an EM class and I'm trying to understand a few things about this derivation. Specifically in equation 18.23 why do we not consider the derivative of the four velocity i.e ##\partial^{\alpha}U^\beta## Then going from 18.23 to 18.25 why is...