Spin Definition and 1000 Threads

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?

Don't know why i put "does is" in the title...oh well... Hey guys, I'm taking Physics in high school and have always been very interested in things such as quantum physics, black holes and the like, but there are a few things that I've been searching for but can't seem to find a non-technical...

Homework Statement consider the possible angular momentum states |s,m>, of a system of two spin-1/2 particles construct all possible states with total spin zero (S=0) Homework Equations The Attempt at a Solution if total S of system is zero, m must also equal zero. So the...

This is more of a question. I don't have a background in physics as you might notice. I am looking for a little help. Why the core spins faster than the crust? At a point the earth’s rotation was much faster, both core and out layers pretty much at the same speed. Both the moon and space...

What are the eigenfunctions of the spin operators? I know the spin operators are given by Pauli matricies (https://en.wikipedia.org/wiki/Spin_operator#Mathematical_formulation_of_spin), and I know what the eigenvalues are (and the eigenvectors), but I have no idea what the eigenfunctions of the...

I am reading Griffiths and I am having trouble interpreting the results of measuring the x component of spin on a spin-up particle. If you have a spin up particle, my understanding is that it is assumed to be up in the preferred axis, z. I would think that measuring its x component should...

hi, I try to use the Noether theorem to determinate the angular momentum of the electromagnetic field described by the Lagrangian density L=-FαβFαβ/4 After some calculation I find a charge Jαβ that is the angular momentum tensor. So the generator of rotations are (J^{23},J^{31},J^{12}) =...

I just read a couple articles on angular momentum and spin... So what is the difference between the spin of a planet on its axis and the spin of an electron on its axis(because they both have angular momentum, right?) Also, if it is the spin of an electron that creates and determines magnetism...

Hello Physics Lovers, I was working and suddenly got this question. What external forces have effects on electron spin, like slowing down/speeding up? Is that a possible thing in the first place?

Homework Statement We have a system of 2 indistinguishable spin-1 bosons. We shall adopt the center of mass frame. Let S = total spin L = relative orbital angular momentum J = L+S = total angular momentum Prove that J = 2m where m is an integer. If given that J=1, what are the permissible...

I'm currently reading the Griffith book and he dosen't really explain this, do i just miltiply the spin kets with the wave function??

I cannot quite understand why expression \frac{1-\gamma_5 \slashed{s}}{2} is covariant? We defined it in the rest frame, and then said that because it is in the slashed expression, it's covariant, what does that mean? s is the direction of polarization, s \cdot s = -1

I don't have a good grasp of "spin along axis" topic, so pardon my dumb questions: 1. Does a photon/electron have a different spin across each of the 3 axis? i understand that the spin of an electron/photon is not the same as that of, say, a ball 2. Gravity can distort time-space (and hence...

What does this mean? " spin +1 ("triplet") and is thus a boson." Hey, Can anyone explain the best they can what the following means? Its in response to a question I asked about a certain substance. " spin +1 ("triplet") and is thus a boson."

Hi I am studying how the spin orbit interaction in certain materials can lead to topological insulator effects and realize it has something to do with the effects of the SOC on the band structure of the material (Bi2Se3), possibly due to the inversion of the valence and conduction band but I...

When constructing the Lie algebra of the Lorentz Transformation, the references usually start with an infinitesimal proper-orthochronous transformation, and then find the infinitesimal generators. Let's call the set of these generators L. after finding L, the references usually compute the...

I should Use the fact that in general the eigenvalues of the square of the angular momentum operator is J(J + 1)h and show the spin of the electron. I have J= L+S and J2 = L2+ S2 Homework Statement But how could i find the spin of the electron

In Perkins's Introduction to High Energy Physics, the author obtained the spin of neutral pions from the decay \pi^0 → 2\gamma He argued that the z-component of the total photon spin in the above decay can have the value S_z=0 or 2. If s_\pi=1, then only S_z=0 is possible, and the two-photon...

It seems as though many of the threads on this site deal with issue of what the concept of "spin" actually means. I think it may be useful to devote a thread designed to solicit out of the community just what this property of fundamental particles is. Intrinsic angular momentum as opposed to...

Quote from wikipedia about the electron's spin But in optics and other fields we learned that speeds exceeding c are possible, if they do not propagate information. So is the concept of a classical electron with definite radius still physically correct in the sense that it's surface is...

If spin particles are in \vec{B} = 0, then is it impossible to determine their magnetic moment at a given time given any investigative method?

A friend of mine was reading Penrose's new book on CCC; I do not want to discuss this story here but a rather interesting detail which could be relevant w/o the whole CCC stuff. SR and GR rely on (global and local) Lorentz invariance. From these symmetries one can derive invariant mass M² and...

Hi there. I have to solve this problem. The statement says as follows: A particle beam with l=1, without spin and with momentum p is incident on the plane x= 0. In the region x<0 the particles move freely and for x>0 are under the action of a constant magnetic field H in the z direction V(x) =...

Not sure if the question makes sense, nevertheless it can help clarify some concepts, I guess. What is the amount of energy required to change the spin (intrinsic angular momentum) of a photon?

When we speak about wave function of an electron, we write it as ψ_{n,σ} (x,ζ) so that we specify here the orbital quantum number by n and spin quantum number by σ. σ can take two values according to spin up or down. x is space position and ζ has two discrete values related to spin up and down...

Dear Forum, I would like to understand what the origin of spin 1/2 is. I read in Feynman's lectures that the origin is related to quantum field theory. I know nothing about quantum field theory. Is there an easy explanation? Thanks Cabrera

In relativistic limit the spin and the angular momentum are not of conservation because of spin-orbit interaction.Then the symmetry SU(2) is broken because vector spin does not commute with the interaction Hamintonian.The SO(3) symmetry is also broken for the same reason.So I do not understand...

I'm currently taking a first course in quantum mechanics and we just recently introduced generalized angular momentum. Now, take the special case of a spin-1/2 particle. If i understood this correctly there are two possibilities spin up: ms = 1/2 , and spin down ms = -1/2 , this comes from...

I know that the generators of the Poncaire group that are associated with *orbital* angular momentum belong to an infinite dimensional representation, i.e. \begin{equation} L = \frac{\partial}{\partial \theta} \end{equation} Also the spin generators are associated with some finite...

Homework Statement A light string can support a stationary hanging load of 27.0 kg before breaking. An object of mass m = 2.81 kg attached to the string rotates on a frictionless, horizontal table in a circle of radius r = 0.809 m, and the other end of the string is held fixed as in the...

Positronium annihilation opportunities are strongly restricted by the requirement to conserve spin. The spin of a photon is 1; and for some reasons two photons are completely unable to have spins in different directions. They can only have parallel spins (total 2) or antiparallel spins (total 0)...

Homework Statement The z-component of the spin of an electron is measure and the value h-bar/2 is found. Immediately afterwards, the spin along a direction making an angle θ with the z-axis is measured. What are the possible outcomes of this second measurement and with which probabilities do...

So in my quantum class we learned that if you measure spin in one direction and get h/2 and then in another direction that it will be (plus or minus)h/2 as well. I was wondering how you would know the probability of it being the positive value vs the negative value. It's a function of the...

Does the cooper pairs spins (up and down) cancelling out have anything to do with anything? Is the current spin polarized in a superconductor?

I’m a layman who has reviewed some popular literature on QM. Apologies in advance for my naivety. I’m of the impression that the quantum spin (±½) of an electron can be determined as it travels through a Stern-Gerlach apparatus (SGA) for the single direction in which the SGA is aligned (say...

What does the spin of an electron mean? Is it the z component of the spin angular momentum or the spin quantum number?