Spin Definition and 1000 Threads

As we know, spin is an internal symmetry. but it seems a bit different from other internal symmetry, e.g. electrical charge, color, flavor... because it can be coupled with orbital angular momentum and in some aspects be linked to space-time. further more, we can classify all the particles into...

Is spin the only physical parameter that can be entangled? If not, what else? If so, it seems there is something special about spin?

This is a bit embarrassing, but by convention does |0> = (1,0)^T and |1>=(0,1)^T, where we are in the basis of the eigenvectors of \sigma_{z}?

I don't know if you are familiar with it, but in pertubationt theory for hydrogen it is handy to look for eigenstates of J = L + S since this commutes with the hamiltonian (L and S are not separately conserved). My book then says that the good quantum numbers are: n,l, j, mj I must admit I'm...

I have been reading up on spin networks and spin foams... but most of the publications seem to come from 1999 or 2000. Does anyone know what happened to this idea? Is it still valid, or was it a dead end? Is it still an active area of research, or did the idea perhaps evolve into something with...

Homework Statement I put this in the math forum because although it's for my EM waves class, it's a math question. Show that the spin force can be written as: F_{spin}=\frac{-1}{2}Im(\alpha)Im(E\cdot\nabla E^{*})=\nabla\times L_s Find L_s. Where \alpha is complex. I'm using E^{*} to denote...

Homework Statement Consider an electron, described initially by psi = 1/sqrt(10) with column vector (1 3). A measurement of the spin component is made along a certain axis, described by operator A, it has the eigenvalues +h/2 and - h/2 as possible outcomes, and the corresponding eigen states...

I have a question about how my book derives a formula. It starts with: We have an electron free too move on a cylinder and from the cylinder there is an electric field pointing radially outwards. Now for an electron moving in an electric field it sees local magnetic field given by: B =...

If two quarks are in a S=1 state, are they in either ##|\uparrow \uparrow \rangle ## or ## |\downarrow \downarrow \rangle ## ?

I seem remember hearing that spin-1 was ruled out but since reading this paper I am unable to find any info on spin-1 Higgs. Has there been any further developments on this? Honestly, I am not a particle guy so I'm not sure on the details... can someone explain why Higgs' particle has to have...

Energy function ##E=-S_1S_2##. I took ##J=1##. If spin are oriented parallel energy is negative. How could energy be negative?

I am very much familiar with the Lorentz force. From what I know, that is HOW a moving charge in a magnetic field gains centripetal acceleration. My question is this : Is there any explanation over why a moving charge in a magnetic field moves in a circular motion? I know the magnetic field is...

Suppose you have an electron and a proton, which both can have either spin up or down. The possible combinations are: \uparrow\downarrow, \downarrow\uparrow, \uparrow\uparrow, \downarrow\downarrow But for some reason my book only allows a linear combination of the two first since they both...

Can we approach spin by gradient. For example, spin 1/2 can be written as 180 degree turning in 360 degree space while spin 2 is 720 degree turning in 360 degree space? If I have a ball spinning with angular momentum perpendicular to rotation plane, what is the spin value of the ball? Can some...

Hello, Fermions have a +1/2 and -1/2 spin. Is there any reason for that or is it just an intrinsic property?

Hello! I couldn't find any answer to a wondering I have: On one end of a light string, attach a heavy ball, and on the other end of the string hold it with your hand and whirl around the ball-on-string. You reach a high rotational speed and finally the string breaks at the string-ball...

Heyy! Please check the attachment and explain why are they arranged (the matrix entries) the way they are? I mean, what is the rule for building up a matrix? In other words, why did not we start with <-1/2, -1/2 l S^2 l -1/2, -1/2 > and placed it as being the first entry? Thanks.

Hi I'm trying to understand how the sum over spin polarizations is treated when using the Narrow Width Approximation(NWA) with a spin 1 resonance. For a spin zero resonance there is no such problem and the factorization is quite straightforward. I'll go through some details to explain where...

Hello! I have done some quantum mechanics, quantum field theory and general relativity. Not much, but enough to say that I have the big picture. Aside from this I have read about analysis on manifolds, functional analysis, Lie algebras and topology. Now there is a red book in my bookshelf...

This is an exciting development in LQG. They have a proposal for how to generalize the ideas of spin network and spin foam so that the network vertices are made of chunks of noncommutative space instead of ordinary space. I'd be glad if anybody who's looked at the paper and wants to volunteer...

Hey, I'm having trouble interpreting a question, as the solutions say something different... Anyways the question part d) below: So we want to determine the expectation value of the y-component of the electron spin on the eigenstate of Sx, now I would of thought this was given by...

As far as we know, an electron cannot be decomposed into angular momentum of constituent parts. So how am I suppose to be thinking about what "spin" is? I've come across intrinsic angular momentum explanations, but I'm not really satisfied with that and am still a bit stumped.

what is the formula of spin connection in GR ? can we show it in term of structure coefficients ?

Homework Statement Calculate the spin wave dispersion relation Ek for the ferromagnetic Heisenberg model with jtot = 1/2 Assume a 1d square lattice and interactions of strength J between nearest neighbours and zero elsewhere Homework Equations H|k> = [E0 +2jtot\sum J(r)(1-Exp(ik.r) ]...

hi i have a doubt about magnetism i am assuming that magnetism is caused by spinning electric flux if we change the velocity(voltage) of the electron does the spin increase? how can we calculate spin of the electron which forces are responsible for electron spin

Hello, For two spin 1/2 identical particles, the triplet state is: |UP,UP> 1/√2 (|UP,DOWN> + |DOWN,UP>) |DOWN,DOWN> Q1: in the up,up or down,down, are the two electrons considered to have the same spin quantum number? Q2: If so, then only the middle one (see above) is where they have...

Consider a ball tethered to a post by a string. The faster it spins, the higher it gets until the bAll is the same height as the place that the string is attached to the post. What force accounts for this?

E.g. electrons. From other posts and Wikipedia, it apparently isn't the speed at which the particles rotate, so what the heck is it?

One may have noticed from my recent posts that my head has been spinning lately, or more specifically, I’ve had spin on the mind. It is a frustratingly puzzling piece of the picture I’m trying to wrap my head around. Here’s the latest mind bender I’ve been grappling with. Although...

I’ve heard in several places that we must view the spin of subatomic particles not as we would that of a classical object since, if we did so, we would find that the velocity of the spin would be so great as to violate the light speed limit to achieve their magnetic moments or whatnot. Can...

I've been reading Griffith's Introductory text on quantum mechanics, and I'm afraid I've hit a major roadblock. I don't understand his section on spin at all. I get the part about there being no classical analogy of quantum mechanical spin, but then he goes on to develop the algebraic theory of...

hi pf, i got following questions in my mind while reading about the spin angular momentum of an electron. 1. From rotational dynamics we know that to have angular momentum a body must necessarily rotation or motion? so does an electron rotates as it has spin angular momentum or does it...

Homework Statement A spin-1 particle is placed in a constatn external B field with B_0 in the x direction. the intial spin of the particle is spin up in the z direction. Take the spin Hamiltonian to be H=\omega_0 S_x determine the probability that the particle is in the state |1,-1>...

Homework Statement Homework Equations The Attempt at a Solution I have totally no idea how to solve this question. But I find it somehow similar to the Larmor precession problem. Therefore I try to solve my problem by referring to that. Are there any mistakes if I do it like...

Homework Statement Homework Equations The Attempt at a Solution I don't know what's wrong with my work. I can't obtain the eigenvector provided in the model answer. My work Model Answer

The Pauli-Lubanski spin 4-vector for a particle in its rest frame is given by Sμ = (0, Sx, Sy, Sz). (Note this is the version from Rindler, which defines S in terms of the 4-velocity instead of 4-momentum) From the 3 spatial components, it is easy to construct a unit vector that points along...

I have bumped into a term a^\dagger \hat{O}_S | \psi \rangle I would really like to operate on the slater determinant \psi directly, but I fear I cannot. Is there any easy manipulation I can perform?

I am a High School student and I was told that magnetic field appears whenever you align the electrons around the atoms (when they spin in the same direction around their axes). Is this true or do schools actually mislead people?

I have a few basic questions about the Pauli-Lubanski spin 4-vector S. 1. I've used it in quantum mechanical calculations as an operator, that is to say each of the components of S is a matrix operator that operates on an eigenvector or eigenspinor. But my question is about the utility of S...

Since spin is a separate variable in a wave function, independent from its location in spacetime, why isn't it considered a dimension beyond the 3+1 of spacetime?

Looking at the Standard model, I noticed that all the quarks and leptons have a spin of 1/2 and all of the gauge bosons have a spin of 1. Can someone give me a general definition of what "spin" is and the difference between a particle that has a spin of 1/2 and a particle that has a spin of 1?

Homework Statement The 3-dimensional harmonic oscillator potential holds N identical non-reacting spin 1/2 particles a)How many particles are needed to fill the low lying states through E=(3+3/2)\bar{h}ω b)What is the total energy of the system c)what is the fermi energyHomework Equations...

I understand that we are not to think of an electron literally spinning on its axis because the equatorial speed would far exceed the speed of light. However, just for fun, I've been trying to find out just what the speed would be to make the numbers come out to agree with the observed angluar...

Does a Lorentz boost change the "direction" of an electron's spin orientation? For example, if an electron is in a state "spin-up" along x, and this electron is subjected to a large boost along another direction, say z, will the electron's spin remain "spin-up" along x? What if the...

I have questions regarding the physical interpretation of Dirac 4-spinors. Using the Weyl/Chiral representation and the electron as the particle, in the rest frame of the electron, the 4-spinor reduces to two identical 2-spinors, that is to say the 4-spinor takes on the form (a b a b)...

This has been a contradiction in my brain for some time. If I want to rotate one nuclei (spin 1/2), with say an applied magnetic field B and RF pulse (at the appropriate larmor frequency), how does the spin actually rotate? I thought it can only take on discrete values of 1/2 or -1/2...

I asked this question in Yahoo Answers but I didn't think that the responses were very good This is just for my own knowledge I wanted to know if let's say for instance that I had a rotary device, clamp right on the center of mass of my phone and it spun rapidly... could the phone spin so...

Hi everyone. I'm trying to give myself a primer in quantum mechanics/chemistry as I'm doing a literature review on NMR and its applications. I have a few questions. (I'm an electrical engineer, I understand our troubled past, and hopefully our peoples can find a peace) I'm trying to...

Homework Statement Homework Equations The Attempt at a Solution I am just trying to figure out how to start the problem. Any help would be greatly appreciated.

What's a pin 1/2? How can one spin 2 whole revolution to get to the same side? I don't get it. How about spin 0,1,or 2. What do those mean?