Spin Definition and 1000 Threads

In experiments with polarized beams of particles, I suppose one knows the spin orientation probabilities of those particles, is that the case? When physicists make experiments with polarized beams of unstable particles, how do they treat spin in a decay of such a polarized particle? If the...

As I understand it, the spin of anything is with respect to the background spacetime. So I have to wonder if the spin of elementary particles depends on the background metric, on the number of dimensions of the background, or the expansion rate, or the curvature, etc. Or is spin independent of...

Does photon has spin induced magnetic moment? I think the answer is no. But why? You know, electron has. Does this have something to do with the fact that electron is massive while photon massless?:confused:

Homework Statement A tennis player slices the ball to spin and deviate from its normal parabolic path. What is an explanation for this phenomenon? I am having trouble visualizing the phenomena that is occurring with the slice and as well as the explanation give by the book. How is the...

How come normal current has a magnetic moment if 50% of electrons have spin up and 50% have spin down. Is it because they have to be in pairs? Would a wire of current with electrons all polarized up attract a wire next to it with electrons all polarized down? Extra question How come...

Homework Statement |\psi >=a|z>+b|-z> find <S_x > The Attempt at a Solution So I just need to find <S_x>=({|<x|\psi >|}^2-{|<-x|\psi>|}^2)\frac{\hbar}{2} right

Help please! Where can I start if I want to learn Quantum Spin Hall Effect? I have learned the some fundamental ideas of integer quantum hall effect by myself. Under this background, what more should I read? cause I really can't find any notes or videos that are teaching about QSHE. I am now in...

Spin is the art of presenting facts in such a way as to make yourself look good. The best spin, IMO, utilizes accurate facts (to avoid being shown a liar), but utilizes cherry-picking and carefully worded descriptions to paint a picture much more favorable than another view might present. In...

I can't seem to reconcile a part of the vector model of spin and some of its operators. to quote wiki just above the "Bohr model" section: http://en.wikipedia.org/wiki/Vector_model_of_the_atom#Mathematical_background_of_angular_momenta "2.The magnitude of the vectors must be...

I'm currently reading Sakurai's 'Modern Quantum Mechanics' (Revised Edition) and at page 76 he introduces a spin half hamiltonian H = - (\frac{e}{mc}) \vec S \cdot \vec B. But what is c doing in this hamiltonian? Clasically the energy of a magnetic moment in a magnetic field is E = -...

My understanding is that spin angular momentum is just as real as bulk angular momentum. So, if we get the spin of some electrons in an object to flip, then the object should start spinning in the opposite direction to conserve angular momentum. Right? If we mount a permanent magnet in an...

'Ello, I have a question regarding the results in this paper (and another which I will mention later) http://arxiv.org/abs/hep-ph/0212199 Now, I'm not so concerned about the 'braney' bit, but more their definition of the cross section in Eqn. (46). They have included the usual (2j+1)...

Regarding the term "Spin"... I've see a number of different descriptions. In the book I'm currently reading it says it is "loosely" the measure of the strength of rotational motion, and "technically" the measure of the quantity called angular momentum. It also states we consider the spin...

this is from Omnes' book Understanding QM Has this problem been resolved or is it still outstanding?

what do we mean by spin of a particle when we say it a point particle?how do we measure spin experimentally and give it values like +1,+2 etc. what does it mean by a spin 0 particle?

I don't understand this very well...

Hi ! I am working on the modelling of the Table Tennis game. Can I calculate the Spin of the Ball after hitting without using any camera and any vision system. I know the velocity of the ball before and after the hitting in all directions (x,y,z) and velocity of the racket as well. Is...

Hi all, I was just pondering why spin is odd under time reversal. I am trying to get my head around CPT invariance and am failing to find good material online. Thanks

Can there be EM radiation with spin zero? I don't mean that the sum of all spins is zero, as it usually is. My thinking is that all light spins and usually the left and right component is of equal intensity. Am I correct in thinking that light reflecting off of a suitable horizontal...

The "spin family" art works have a model of something with spin 2 1/2. I can't find any particle with this property. The max seems to be the graviton with spin 2. ?

I'm wondering how the spin of a particle, whether a particle is a fermion or a boson... how does this relate to the symmetry of a particle, U(1) or SU(2) or SU(3)? I'm trying to understand SUSY in relation to the other internal symmetries? Is there spin 1/2 and spin 1 particles associated with...

I can't visualize spin... I know that its not just a particle rotating about its axis... Then how do I think of it?

Can we measure the spin of a particle by measuring the force on a Magnet? I wish to consider a modified stern gerlach like apparatus where a Magnet of mass M is attached to a spring. Can we measure Spin of the particle by studying the deflection of the magnet? Even if it is possible, I can...

From what I've learned atoms with unpaired electrons are paramagnetic and those without are diamagnetic. Strontium has electron configuration of [Kr] 5s^2 so why is it paramagnetic?

As a preface to a different question, it is valid to think of the property of spin of elementary and related particles as basically just tiny magnets, right?

I have a problem understanding the Lorentz transformation of the spin. The spin 4-vector is defined in the rest frame of the particle as s^{\mu} = (0, \vec{s}) and then boosted in any other frame according to s'^{\mu} = (\gamma \vec{\beta} \cdot \vec{s}, \vec{s} +...

Spin 1/2--Raising and Lowering operators question Hi, Quick question regarding raising and lowering operators. Sakurai (on pg 23 of Modern QM), gives the spin 1/2 raising and lowering operators S_{+}=\hbar \left|+\right\rangle \left\langle-\right| and S_{-}=\hbar \left|-\right\rangle...

OK I'm super frustrated.. I spent 50min typing the whole text here earlier and click preview only to be told I was logged out. Click back and and all was gone. Damn.. Ok here's the question, AGAIN. Weight: 1kg Type: Flywheel, OD is 80mm, ID is 40mm if that matters. So that's a typical...

In the article, "What is spin", by Hans C. Ohanian we are shown how to take the wave-function for a Dirac electron with spin up and localized in space and then determine the momentum density in the Dirac field. The momentum density divides into two parts, a part that depends on the motion of the...

Hello, I usually just lurk around the forums as a first year engineering student, but I'm 27 years old. I have my bachelor's in Accounting, but I'm not very passionate about it...anyway, that's a whole different thread, but the point I'm getting across here is that my practical knowledge of...

I tried searching through but didn't find this asked. If the spin of the particle detected at LHC comes back as 2, for instance, does it mean it's not a higgs boson? There are 5 higgs in supersymmetry, do they all have spin 0?

Hi, Just a quick question: When people talk about an atom's spin do they actually mean it is physically spinning or is it a word for some different process or property of the atom - if so, what property is this? Thank you for your time.

What is the spin direction of the electrons through the ferromagnetic material? It will become parallel or antiparallel? I was confused because the scattering rate and conductivity both depend on the density of state at Fermi level. For ferromagnetic material, is it right to say that at the...

In General Relativity, the assumption is made that the stress-energy tensor Tαβ is symmetric. However, if there are particles with intrinsic spin, then this assumption is false, as described here: http://en.wikipedia.org/wiki/Spin_tensor The spin tensor Sαβμ satisfies: ∂μ Sαβμ = Tβα -...

Hi, I am scratching the surface of information regarding particle physics. I have a basic understanding of standard model. What I am not quite understanding is what 'spin' is. I know that all fermions have a spin of 1/2, but what exactly is spin? Thanks

Hi, All articles on spin liquids I've seen treat them as insulators. This is understandable in the context in which they were first introduced i.e. the resonating valence bond state in which every electron is singlet-ed with every other, and thus essentially blocking conduction. Given...

Hi friends I've a big andu here. Electron revolts around the nucleus in the circular path. Its due to the force between them. Why the electron spins around its own axis?

Electrons paired up in an orbital have anti-parallel spins. One rotates in clockwise direction and the other in anti-clockwise direction in the same orbital. In that case wouldn't the electrons from opposite directions collide each other? Please don't mind if the question seems silly. But thank...

Which of the following require energy? - change the spin of photon - entangle photons - disentangle photons - change the phase of a photon - change the wavelength/frequency of a photon - cause a delay in path of a photon (by each of the various methods) - change the direction of a...

I have become fascinated by Topological Insulators (TI) and wish to learn more about them. I have successfully used a slab calculation to look at one of the prototypical TIs, Bi2Te3 using the LAPW+LO/APW+LO code Wien2K using a 4 quintuple layer slab. I can see the surface states across the...

Homework Statement two identical particles of spin 1/2 that confined in a cubical box of side L. find the energy and wave function (non-interacting between particles) Homework Equations for a cubic boxby and reducing the Schrodinger equation: ψ(x,y,z)=√(8/L3 ) sin((nx πx)/L)sin((ny...

(without using the intuitive yet eronneous idea of "spin" meaning "spinning")

Hi, If we think of an electron's spin as just being a classical kind of a spin, what happens as it speeds up close to the speed of light relative to a laboratory frame of reference? Does the lab frame see the spin of the particle "slow down"?

Suppose an electron crosses worldlines with me such our relative velocities v are a substantial fraction of that of light. Say the electron's spin is in some state \mid\psi\rangle; for example the doublet state. I would like to know, or read references that describe how to calculate, what...

When I was at Uni, in the 60s, we had a brief course on 'Space Physics'. It had a hotch potch of topics in it and one of them was about actually launching satellites. 'In those days', apparently, vehicles were rotated during the launch and this rotation had to be eliminated once they were in...

How is it that only 1 spin up and 1 spin down electron are allowed in an atom even though there is no measurement to collapse the state function?

So my main area of research is molecular biology and biochemistry, but nuclear and particle physics frequently manages to find its way in it and it's always baffling to me. I've been participating in research on bacterial Cytochrome P450 enzymes; they catalyze the oxidation of organic...

Due to diamagnetism in certain substances such as water, does this cause a faster orbital spin due to the change in magnetic dipole moment induced by an external magnet? I'm doing a Science-fair project at the moment and this is eluding me Thank you

Hi, Everybody! Currently, I am reading the book "Lectures on Quantum Field Theory" (by Ashok Das) But I am a bit confusing. Why does Dirac Equation describe spin 1/2 particles? I have already known that Dirac Equation bears some angular momentum structure, but why it just describe spin...

Homework Statement I use Griffiths and see the example for spin 1/2 to derive the eigenspinor of Sx. I just can't seem to follow how he get from there or how he is measuring the probability for a given state. Homework Equations I have correctly derived the...