Spin Definition and 1000 Threads

Please teach me this: We know that orbit angular momentum is the product of coordinate operator vector and momentum operator,so when we reflect the coordinate system the angular momentum is unchanging(axial vector).But I do not understand why spin vector is axial vector. Thank you very much in...

Why does a force used to twist/alter the spin-axis of a spinning wheel increase when the spin motion increases? Why this Gyro effect?

Hi all, In class I've recently been taught the schrodinger equation and about spin(couple weeks apart). My questions are- 1. In laymans terms, what exactly does the S-eqn mean? What I have taken it to be so far, is an equation that determines the probability of the position of an e- in...

We are starting to learn about spin in my introductory quantum mechanics course, and I was wondering if anyone could provide a physical interpretation of an electron's spin. I understand its a form of angular momentum which has nothing to do with the motion of the electron in space, but since an...

It is said that massive stars spin faster than less massive ones and I am always wondering why.Could someone please tell me the reason? Thanks a lot.

Dear physicist, I designed an experiment for my undergraduate students. As we know, for spin operators, the commutation relation is [Si,Sj]=ihSk We also know, if we use two polarizers which are perpendicular each other, there is no light other side after polarizers. Namely apparatus is...

Is spin of electron taken into account when people accelerate electron in LHC?

When you have an ordinary (read: spin zero) particle with a quantum state |ψ>, the corresponding position-space wave function <x|ψ> is an ordinary scalar function of position. How do things work when the particle has spin? In that case its quantum state will live in the tensor product of two...

Homework Statement Find spin, parity and isospin of second excited state of {}^{10}B nucleus, if we know that the second excited state (at E_x=1.74 MeV) can intensively be excited with reactions: {}^{7}Li(\alpha,\ n),\ {}^{9}Be(d,\ n),\ {}^{9}Be({}^{3}He,\ d), {}^{11}B(p,\ d), and cannot be...

I'm reading about properties of electrons in atoms, and it says an electron's position in an atom can be described by energy level, shape, orientation, and spin roughly speaking: the energy level (n) dictates the radius from the nucleus (probability wise) the shape (l) dictates... the shape...

If I give you a box, completely empty except for one hydrogen atom, could you theoretically measure the spin of its electron to tell me if it is +1/2 or -1/2? If this can be done, how can it be accomplished (at least in theory). Or if the question is complete nonsense, why is that? (Sorry for...

Some friends and I have been having some discussions about why an unfletched arrow will spin right when shot from some bows and left when shot from other bows. We have taken bows and shot a series of different arrows and every arrow out of that bow went in the same direction. So I gues I...

Hi I am working my way through Griffith's Introduction To Quantum Mechanics and I have got to the section on addition of spin angular momenta. I'll copy and paste the bit I'm struggling with, as it's easier than paraphrasing: http://img714.imageshack.us/img714/2783/80183858.png...

modern metal yoyo with ball bearing works totally different with the old. it can spin about 5mins within one throw for some reason. and can it spin about 1min if I throw it horizontally? you may wonder about what is a horizontal throw. then see the video post below. https://vimeo.com/39247415...

Hey Given an anisotropic hamiltonian \mathcal{H} = -\sum_{j,\rho} \left( J_\rho^z s_j^z s_{j+\rho}^z + \frac{J_\rho^{xy}}{2}\left( s_j^+ s_{j+\rho}^- + s_j^- s_{j+\rho}^+ \right)\right) - g\mu_B H\sum_j s_j^z Here \rho is a vector connecting the neighbouring sites. How do I show that the...

Hi all, :shy: Could anyone explain in very simple language, for lower UGrad standard, what spin foams and spin networks are? Thank You. SINCERELY DPA

I was doing some reasearch on electrons, and I found that they have both particle and wave like characteristics. Is this the reason why? because they travel in waves around a nucleus? or am I missing a piece of the puzzel? :smile: Cheers

I think I have a pretty good handle on how scalar field scattering works in QFT, so now I'm trying to wrap my head around spin 1/2 particles, and I'm having a bit of trouble with it. For instance, in N + \phi \rightarrow N + \phi scattering, an application of the Feynman rules leads to an...

Dear forumers, I was thinking about how the Sz operator "couples" (has non zero matrix elements) states with the same expectation values for the projection of spin on the z-axis (duh! α and β are its eigenvectors), and how Sx and Sy couple different states (once again, duh!). I was also...

Hello all, Imagine two spin 1/2 particles that are entangled, going towards two stern-gerlach apparatuses, with some relative angle. Now imagine one stern-gerlach device measures the spin of one of the particles as up. What is the chance that the other stern-gerlach device measures the spin...

I already asked this question on physics.stackexchange.com, but did not get the desired response. I am interested in the opinion of your community. Picture an entangled pair of spin 1/2-spin particles with total spin 0. In the diagram, particle 1 of the pair is moving to the left (-y), and...

In the double slit experiment there are interference terms which are responsible for the way in which particles appear on a screen (diffraction pattern). The density matrix for an electron with spin |+X> going into a stern Gerlach alligned in the z direction also has off diagonal terms which...

Quant.Entaglement:Difference between superposition of spins and not knowing the spin? [SIZE="3"]Let two electrons' (A and B) spin be entangled. They'll be in a superposition of up and down spin. When the spin of A is measured it settles randomly to up and instantly B is set to down. What...

Hi all, Here is what I am trying to understand qualitatively. It is NOT a homework problem: A long, one-dimensional rod of mass M and length L is in free space. There is no gravity, no forces, and no pivot. Its just a rod sitting there, floating, with nothing else around. Let's say its L=0...

Homework Statement We have N particles, each of which can either be spin-up (s_i = 1) or spin-down (s_i = -1) with i = 1, 2, 3...N. The particles are in fixed position, don't interact and because they are in a magnetic field with strength B, the energy of the system is given by: E(s_1...

Hello everybody, I was watching a lecture on quantum mechanics, and the lecturer was talking about the 720 degree rotation required for a spin 1/2 particle to return to an identical state. I'm aware of this, but I was more interested in the experiment to show that there is an actual...

Does Electron spin generate electricity? I know that with the electron spin generates a magnetic field, but does it generate an electricity? Thanks for any input!

Homework Statement The entire problem is quite in depth. But what I am having trouble with is just a small part of it, and it boils down to finding the following commutator: \left[ S_{z}^{n},S_{y}\right] where S_{z} and S_{y} are the quantum mechanical spin matrices. The reason is that I have...

In canonical LQG, unitarity is presumably guaranteed by the canonical formalism. How does one check for unitarity in the spin foam (path integral) formalism? Do the new spin foams pass the necessary tests?

Homework Statement Can someone tell me if the spin on an electron can change orientation as it flits around in our universe? Is the spin confined to specific orientations. or can it the axis shift around in a continuum? For entangled particles, is the spin locked into a specific orientation...

Hello all, I am having trouble understanding how this works. In Krane there arises a discussion on total angular momentum I of the deuteron. While it is true it has three components, namely the individual spins of the neutron and proton, but also the orbital angular momentum l of the nucleons...

As far as I know: the possible orientations that the total angular momentum can take (given my Mj) are degenerate. if we apply a magnetic field, degeneracy will be lost and different states arise. this is the zeeman effect but when looking up on google for zeeman effect, a webpage used as an...

Which experiment does show that electron has a spin of magnitude of \frac{1}{2}\hbar? I guess, Stern–Gerlach experiment shows that electron has a kind of intrinsic spin; because of which, particle beam gets deflected in some specific way under the application of an external magnetic field...

There is an external magnetic field along the positive z direction B = (0,0, B) and the initial spin direction at time t0= 0 is specified by the direction cosines Ŝ0= (cos α0, cos β0, cos γ0) where α0, β0, γ0 are the angles between the initial spin and the x, y, z axes, respectively. This...

There's something I don't think I quite understand about spin and how it acts a generator of rotations. I'll start with quickly going over what I do understand. Suppose you want to do an infinitesimal rotation around the z-axis on some state: \def\ket#1{\left | #1 \right \rangle} \ket{\psi...

Hello 1. I am having some trouble with getting the correct answers when trying to solve problems that involve spin (Problems from textbook Physics for scientists and engineers, Serway & Jewett). I'll give two examples to illustrate: The process p + p -> p + p + n (protons and a neutron)...

Please help a poor stupid layman. When a particle has a spin of 1/2, what does that really mean? 1/2 of WHAT?

Let's say we have identical spinning baseball balls. We catch the balls into baseball gloves. The gloves have different velocities. Some glove may approach the ball from the equator, while another glove approaches from the pole, I mean the pole and the equator of the ball. As the balls have...

So this is my first quantum mechanics class and so far we have spent about a month (well 3 weeks) on just the mathematics. So in my book, the author explores the ideas presented by the stern gerlach experiment. It related the beam of silver atoms traveling through the separators to light...

I have been asking myself of late whether or not the energy of a fundamental (point-like) particle has a component attributable to its spin. My understanding has been that a point-like particle has no energy of spin because its moment of inertia is zero. This article appears to both agree...

I'm attempting to spin cast a parabola, and aim to hang my spinning vessel directly from the driveshaft of a motor to get it to spin as cleanly as possible. Are there any PWM (12v ideally) 10-100rpm dc motors than could support 10kg thrust load? I would strongly prefer to not use gear systems...

Homework Statement A beam of neutrons traveling in the x direction initially has all its spins up along the z direction. The neutrons pass through a region in which there is a uniform 1 tesla magnetic field in the y direction. What is the minimum time t the neutrons need to remain in the...

In QM and QFT, imaginary time is used to make the oscillatory path integral converge, and also to handle terms that are not semibounded in Minkowski spacetime. In CDT, imaginary time is also used after the path integral is restricted to "causal" configurations. How is the oscillatory...

Homework Statement What is the shell model spin and parity of _{38}^{89}Sr? 2. The attempt at a solution If i fill the levels as we usually do, Protons will end up in the level 1f_{5/2} with 6protons,ie the level is completely filled If the neutron number is considered,1g_{7/2}...

this sounds like a question that should be answered somewhere, but i can't find it. how many quantum numbers does it take to specify the state of a spin 1/2? 1. if it points along z, then just 1: the eigenvalue of Sz will do (up to global phase) A. whether or not in a B field B. if...

Hi guys ! Im trying to get my head round precession, nutation and spin. Suppose I have a cylinder of height L, base radius R. Initially it is just spinning about its central axis (i.e. line joining cone tip to the centre of base). In this scenario, centripetal acceleration experienced by say...

While attempting to wrap my head around the classical Twin Paradox, I asked myself the following. So far I have not been able to reach a well reasoned answer... which is no big surprise. :) Twins (A and B) are oriented in space such that A could be said to be standing on B but facing in the...

Hi there, I apologise that I should probably know this/its a stupid question but I seem to have forgotten all physics over the holiday and so any help would be great! I have been told that there is a beam of atoms with spin quantum number 1/2 and zero orbital angular momentum, with spin +1/2...

By "spin" we sometimes refer to spin angular momentum, sometimes we refer to a specific representation of Lorentz group, in the following I'll refer to the former, otherwise I'll write "spinor representation" Say an spin up(z direction) electron at rest, state vector |m,+\rangle being an...

I think I understand the gist of it. Is it a property that exhibits properties of angular momentum, without actually spinning, because it isn't made of anything else as far as we know, and has no inner structure?