Fundamental characteristic property of particles which together with orbital angular momentum acts as the generator of rotations and which doesn't have a classical equivalent but is sometimes compared to and contrasted with classical intrinsic angular momentum.

learn more… | top users | synonyms (1)

0
votes
0answers
11 views

Spin operator in an arbitrary direction

let $\ \hat{n}=(\sin{\phi}\cos{\theta},\sin{\phi}\cos{\theta},\cos{\phi})$ How to prove $\vec{S}\cdot\hat{n}$ is the spin operator in an arbitrary axis rigorously?
-1
votes
0answers
38 views

Is mass in the sub-atomic particles caused by their angular momentum? [on hold]

When they found the God Particle, they said it's responsible for creating mass in all other particles except photons and neutrinos. But how it creates mass is a mystery to me. My suspicion is that ...
0
votes
1answer
38 views

How to show the finite rotation of a spin-1/2 system?

I'm reviewing my quantum mechanics by going through Sakurai and Napolitano again and working out all of the derivations. I'm stumped (though I probably shouldn't be) on some algebra in the finite ...
1
vote
1answer
28 views

Generate exciton with parallel/anti-parallel spin

How can I experimentally generate excitons, controlling the spin-polarization of the participated electron and hole to be either exclusively parallel or anti-parallel?
-2
votes
0answers
56 views

Entanglement (spooky effect) [closed]

I watched some videos on this subject, and I have seen that a particle may have "spin up" or "spin down" and if one has spin up, the other has spin down when we measure it. My question is: do we ...
1
vote
1answer
44 views

What is polarisation, spin, helicity, chirality and parity?

Polarisation, spin, helicity, chirality and parity keep confusing me. They seem to be related, but exactly how they are related is unclear to me. Can someone maybe give a short overview about what ...
1
vote
0answers
43 views

Transfer from Heisenberg to Ising model

It is well know, that ferromagnets can be described using Hamiltonian $$ H = -\sum\limits_{i<j}J_{ij}\, (\mathbf{s}_i \cdot \mathbf{s}_j). $$ where (three dimensional) spins $\mathbf{s}_i$ ...
1
vote
3answers
49 views

Does unpolarized light means that photon is in superposition state?

I read that a polaroid filter is made of many long chain of molecules aligned in one direction and will only allow the vibration of light with the same alignment as the filter to be absorbed. I ...
3
votes
2answers
64 views

How can I use a magnet to lift a paperclip?

This question has been asked already, but no satisfying answer came up. All the answers seem to push the problem further, but do not explain clearly what is going on. I will reformulate it for a ...
1
vote
1answer
58 views

Decomposition of tensor product space into direct sum [closed]

Consider a tensor product space of two representations $j = \frac{3}{2}$ and $j = 1$. How to show $4 \otimes 3 = 6 \oplus 4 \oplus 2$?
1
vote
1answer
81 views

How do I interpret/make sense of atomic density plots?

For example, this one: I'm familiar with probability density functions, basic quantum mechanics, however, I don't know how to make sense of the chart. Specifically: Are the three numbers in the ...
0
votes
1answer
31 views

Does the electromagnetic force “split” at lower than normal energies?

Since we have working models for forces "combining" or being describable via a single framework at higher energies (such as the "electroweak" force and the aim of GUTs), does electromagnetism split ...
3
votes
1answer
86 views

Why don't antiparticles have antispin?

Antiparticles are often said to particles moving backwards in time. However if they are moving backwards in time shouldn't they also "spin backwards", meaning they should have negative or antispin? ...
2
votes
0answers
22 views

How do phonons and spinwaves interact? [closed]

What governs the coupling of acoustic phonons to transverse and longitudinal spinwaves? Is there a simple picture?
1
vote
0answers
7 views

process of spin trapping in EPR [closed]

How does the process spin trapping in Electron Paramagnetic Resonance [EPR] work? How's it done and what are the challanges?
0
votes
1answer
31 views

Z coordinate expectation value of the Hydrogen atom

I want to find $z-coordinate$ expectation value $\textbf{<z>}$ of the Hydrogen atom wave function $\psi_{1,0,0} = (\pi a^3_0)^{-1/2}e^{-r/a_0}$ in its ground state. I read in some text that ...
5
votes
0answers
45 views

What is the momentum canonically conjugate to spin in QM?

In Kopec and Usadel's Phys. Rev. Lett. 78.1988, a spin glass Hamiltonian is introduced in the form: $$ H = \frac{\Delta}{2}\sum_i \Pi^2_i - \sum_{i<j}J_{ij}\sigma_i \sigma_j, $$ where the ...
0
votes
0answers
22 views

Theoretical model of MRI scanner

Recently I have gained strong interest in studying the Physics of an MRI scanner. Most of the physics resources I have found are strongly practically orientated and do not so much approach the ...
0
votes
1answer
19 views

Larmor Frequency for Spin Transition

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/larmor.html Consider the process of Larmor precession of the magnetic moment associated with the spin angular momentum of an electron inside a ...
3
votes
1answer
90 views

Why is there no 1/3 spin? [duplicate]

Why do no particles have a 1/3 spin? Why are all particles' spin either a half-integer or integer? How would a particle with such a spin behave, as a fermion, boson, or neither?
1
vote
0answers
22 views

Spin of a gauge field

I was wondering what is the simplest way to understand the reduction of the Wigner's little group from $SO(d-1)$ to $SO(d-2)$ when one considers massive and massless fields respectively (in a $d$ ...
1
vote
1answer
29 views

Magnetocaloric Effect and Quantum Spin Relationship?

I watched few videos and read few articles on Magnetocaloric Effect. Basically, some materials, like Gadolinium, heat up if simply placed in magnetic field. But I can't get the explanation they are ...
2
votes
1answer
72 views

What is spin in QFT, non-relativistic QM, and classical physics? When can we ignore spin? [closed]

In section 4.1.1 of quantum field theory book by M. Schwartz, the author wants to calculate electron scattering by photons and writes the following interaction: $$ V= \frac{1}{2}e\int dx ...
2
votes
2answers
77 views

Why can the spin of a relativistic particle not be orthogonal to its momentum?

I have read that the 3-momentum of a relativistic particle cannot be orthogonal to its spin 3-vector. When thinking about how the spin vector transforms when the particle approaches light speed, it ...
0
votes
1answer
31 views

Distance and pattern on Stern-Gerlach experiment

On Stern-Gerlach experiment Is their any experiment data showing the patterns for various distances from magnet to screen? I want to find out if the pattern smaller or not when the screen closer to ...
1
vote
0answers
56 views

The pattern on Stern-Gerlach experiment

I got this picture from following site. http://hyperphysics.phy-astr.gsu.edu/hbase/spin.html See two red circles I added. Two patterns are same. Is it wrong drawing? (pattern in right red ...
0
votes
0answers
37 views

Question about CSCO for identical 1/2 spin particles?

I have two, identical 1/2 spin particles which interact through the hamiltonian $$H = \frac{p_1^2}{2m} + \frac{p_2^2}{2m} + V(|\vec{r_1}-\vec{r_2}|) $$ and I have to determine the observables that ...
-1
votes
1answer
82 views

Spin (for chemists) for 100th time here on the forum [closed]

EDIT: Okay so I see the question was bit unclear. I know about matrices as far as we have used them but we never used any group theory. Determinants like slater determinants are used in chemistry, ...
1
vote
1answer
41 views

Finding the proportionality constant of the Quantum Angular Momentum raising operator $T_{+}$ [closed]

This is a question about the mathematics of angular momentum operators in Quantum Mechanics- specifically a recursive relation from Robert Cahn's Semi-Simple Lie Algebras and their Representations ...
3
votes
0answers
49 views

In quantum descriptions of atoms why are observables (which we derive from the wave function) attributed to electrons?

For example the orbital angular momentum, for the hydrogen atom. Is this the total angular momentum of the atom(electron and proton) or just the electron? I am asking because, I am learning about how ...
0
votes
0answers
20 views

Can an electron change its spin between multiple Stern-Gerlach experiments?

If you run multiple Stern-Gerlach experiments on a single electron, can its spin change in between them? So, for example, could an electron have an up spin through one experiment then a down spin ...
1
vote
2answers
63 views

Rest mass energy of electron

For electron's energy why we some time use the word "REST MASS ENERGY" why we use this word as electron is always spinning? ...
0
votes
0answers
41 views

Spin-1/2 rotation operator: rotation about an angle of $\pi$

The spin-1/2 rotation operator: $$ R_{n}(\alpha) = \begin{pmatrix} cos(\frac{\alpha}{2})-in_{z}sin(\frac{\alpha}{2}) & (-in_{x}-n_{y})sin(\frac{\alpha}{2}) \\ ...
0
votes
0answers
16 views

What can be simple model for spin-polarization of current?

Consider the following structure layers in a wire. The ferromagnetic (F) region is fully magnetized in upward direction. Suppose unpolarized current enters from the left of the junctions. (1) So ...
1
vote
0answers
47 views

What does radiofrequency really do in NMR & MRI?

In NMR, the protons’ frequencies are affected by the magnet which makes them precess around its magnetic field so now all protons will have different frequencies according to their environment ...
2
votes
1answer
115 views

Can different components of a wavefunction become entangled with different systems?

Imagine a $z$-basis spin Stern Gerlach experiment where a single particle is put through the apparatus. The output is a spin state vector consisting of the sum of the two $z$-spin states. Each spin ...
4
votes
0answers
99 views

Classical proof of the gyromagnetic ratio $g=2$

I was reading Representing Electrons: A Biographical Approach to Theoretical Entities, by Theodore Arabatzis. At a certain point, where he is explaining the history of the magnetic moment of the ...
1
vote
1answer
71 views

How force get transmitted when a magnet attracts iron?

According to particle physics , every fundamental force has its force carrier particle. Photon is a force carrier particle of electromagnetic force but how does force gets transmitted when a iron is ...
7
votes
1answer
108 views

Entanglement and the Pauli exclusion priciple

Could you say that two electrons in the ground state of a helium atom experience quantum entanglement? They are both in the same energy level and cannot have the same quantum numbers. If one is spin ...
0
votes
0answers
19 views

Is there a geometric interpretation to the orientation of the spin vector of a spin $1$ atom after passing through a Stern-Gerlach magnetic filter?

When a spin $\frac{1}{2}$ atom passes through a Stern-Gerlach magnetic filter, the atom's spin vector is aligned to be in either the upper hemisphere or the lower hemisphere. This makes good sense ...
2
votes
0answers
58 views

Does the spin of an electron change when transferred from one atom to another?

Some atoms form bonds when they are given energy to create an excited state.From what I have learnt, every electron is assigned a specific spin quantum number. What I am curious to know,is that, is ...
2
votes
1answer
40 views

Nahm's theorem and related with SYM ;other theories

To study $S$-duality in more detail, i tried to read, Electric-magnetic duality and the Geometric Langlands Program. In section 2.1, there is a comment about 10d SYM. Excerpt from the paper above, ...
1
vote
1answer
66 views

Direct Sum representation of multiple particles in Quantum Mechanics

Suppose that I have three non-interacting spin-1/2 particles such that I can represent the combined system in a basis of \begin{align} D^{(1/2)}_1 \otimes D^{(1/2)}_2 \otimes D^{(1/2)}_3 & ...
0
votes
0answers
34 views

Density matrices & spin correlation

So I have two 1/2 spin systems A and B in a singlet state $|ψ>=\frac{1}{\sqrt{2}}(|\uparrow \downarrow>−|\downarrow \uparrow>)$ . The question is: If I measured B and got $S_{Bz}=\hbar/2$ . ...
1
vote
2answers
56 views

How do you determine if the spin is up or down?

Fundamental particles such as quarks and leptons can have a spin either up or down. These spins are (obviously) opposite of each other. But what differentiates them? Let's say you examine a pair of ...
0
votes
0answers
55 views

How many eigenstates for four (non-identical) spin 1/2 particles?

Question Consider a system of four non-identical spin 1/2 particles. Find the possible values for the total spin and state the number of eigenstates for each of these. Attempt So I coupled S1 and ...
2
votes
1answer
55 views

What does Kaluza-Klein theory say about the attraction/repulsion of opposite/same charges?

Since Kaluza-Klein theory is made out of general relativity - a gravitational theory in 4 dimensions which is only attractive, then how does it takes into account the attraction/repulsion of ...
7
votes
0answers
156 views

In a universe with four spatial dimensions would there be elementary particles with intrinsic isoclinic spin?

Elementary particles have an intrinsic property called spin which is different from classical spin as it does not involve actual rotation and the magnitude of spin cannot be changed but particles with ...
2
votes
0answers
45 views

Would CP Violation happen in a universe with four spatial dimensions?

The weak force is the force that violates CP symmetry as the way it effects a particle depends on that particles handedness. Particles have a property known as spin although it is different from ...
1
vote
1answer
68 views

In what physical situation would the correlation of two spins be useful?

I have done problem 4.50 from Griffiths' Quantum Mechanics (2nd ed), quoted below, and got the correct answer. What would be a physical situation where this would be useful? I have already had some ...