Spin Definition and 1000 Threads

Suppose we have a Stern-Gerlach apparatus through which we send spin-1/2 particles and subsequently measure their position. If a passing particle "collapses" to the spin up state about X, it moves "up" and is registered by detector U, otherwise it "collapses" to the spin down state about X and...

Homework Statement Homework Equations The Attempt at a Solution To be honest I'm clueless. I've missed a large amount of the course and just struggling to find any sources that explain this. I don't want the answer to the question, I want to figure that out for myself. What I really need is...

I read somewhere that a magnetic field is caused by the spin of a charge particle, in most cases the electron. So, I take it then that the electrons in the eddy currents in a bar magnet are all spinning in the same direction? Also, do those eddy currents induce currents in the virtual electrons...

I'm studying electron spin/magnetic field and I was taught electrons can have only 2 spin orientations, as seen in the Stern and Gerlach experiment. But this orientations are given in relation to what? Do all electrons in the universe have the only 2 same orientations, or only the electron in...

I'm learning about NMR and it's been stated that deuteron has a spin 1 nucleus and so should exhibit different behavior. Why? I've heard of electrons having spin, and now protons, but I don't see why the spin of a neutron should matter since it's uncharged. I'm thinking a spin of 1 means...

I was just reading in "Spin physics in semiconductors" by Dyaknonov section 1.2.4, page 4 in the footnote, how the Earth's spin is expected to precess around its orbital angular momentum. Does anyone know if this has been considered as a possible cause for Geomagnetic reversal...

Homework Statement Consider the so-called Spin Hamiltonian H=AS2Z+B(S2X-S2Y) for a system of spin 1. Show that the Hamiltonian in the SZ basis is the 3x3 matrix: \hbar2*[(A,0,B; 0,0,0; B,0,A)].Find the eigenvalues using degenerate pertubation theory. Homework Equations Spin Pauli MatricesThe...

I think I understand this only up to a point. 1. Photon spin is quantized to be +1 or -1 and these represent left- and right-hand circular polarization. 2. A photon can have a superposition of 2 spin states in any proportion. 3. Having probability amplitude of 0.5 of spin 1 and 0.5 of spin -1...

I've been trying to wrap my head around spinors, and I think I'm beginning to understand the mathematical formalism, but one thing in particular continues to confuse me. Whenever I read anything mathematically rigorous on spinors, the authors refer to spinors being associated with isotropic...

I am trying to understand the measurement of spin, in order to understand Bell's paper on the Einstein-Podolsky-Rosen paradox. When we measure the spin of a fermion in the direction of unit vector a, will the result be: 1. a value of either +0.5 or -0.5, and upon measurement, the fermion...

Okay, so I was looking at some ideas of storage based on making electrons spin "up" or "down" to store binary data, and I began wondering two things: 1) How does one change the spin "orientation" (for lack of a better word) of a particle? 2) How does one detect the spin "orientation" of a...

(1,a^2,a^2,a^2)) from the action; \mathcal{S}_{D}[\phi,\psi,e^{\alpha}_{\mu}] = \int d^4 x \det(e^{\alpha}_{\mu}) \left[ \mathcal{L}_{KG} + i\bar{\psi}\bar{\gamma}^{\mu}D_{\mu}\psi - (m_{\psi} + g\phi)\bar{\psi}\psi \right] I can show that, i\bar{\gamma}^{\mu}D_{\mu}\psi -...

In trying to derive the Dirac equation in space-time (1,-a^{2},-a^{2},-a^{2}), I have read that the Dirac equation is (i\bar{\gamma}^{\mu}(\partial_{\mu}+\Gamma_{\mu})-m)\psi=0 where, \Gamma_{\mu}=\frac{1}{2}\sum ^{\alpha \beta}e_{\alpha}^{\mbox{ }\nu}(\frac{\partial}{\partial...

Paulis exclusion principle say that two electrons around a nucleus can't have the same quantum number. Does that mean that, say, two hydrogen atoms with electrons with the same spin can't make hydrogen gas? Or does one of the electrons change its spin?

This may be a basic question, but it's something I'm having a hard time understanding. The Wikipedia article I am reading about spin http://en.wikipedia.org/wiki/Particle_spin seems to be saying that spin isn't really what we think of on the macroscopic scale (ie: spinning on an axis like a...

I have a basic understanding of what particle spin is, but I'm not clear on how how integer spins are different than fractional spin values. I also need help understanding how fractional spins are different from each other (difference between spin 1/2 and spin 3/2) and how integer spins are...

Homework Statement Spin-system: A spin-system has N = 30 localized particles with spin quantum number s = ½ and magnetic moment µ0. m = M/µ0 is the magnetic moment M in vertical direction (ms = +½) in units of µ0. Calculate the probability PN(m) for the total magnetic moment M to achieve...

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 ?

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...