What is Spin: Definition and 1000 Discussions

I am trying to add the magnus effect to a golf simulator program but am getting stuck on the coefficient of lift. What are the units I should be using in these calculations? The rest of my program I use SI units. But I seam to get weird results when using them with these equations. Spin factor...

Hi, everyone. I'm trying to get the next identity It is in the format <j1, j2; m1, m2 |j, m>. I hope you can help me

Solving 1D Dirac equation there are 2 matrixs, and from those we get the space probability and current. If that current reflects the spin state, could happen than the EM fields from the matter acting as potentials, drives the spin to up or down, and when it reaches the north os south pole in...

After computind dirac 1D equation time dependant for a free particle particle I get 2 matrixs. From both,them I extract: 1) the probablity matrix P =ps1 * ps1 + psi2 *psi2 2) the current matrix J = np.conj(psi1)*psi2+np.conj(psi2)*psi1 I think that current is related to electricity, and...

I derive the quadratic form of Dirac equation as follows $$\lbrace[i\not \partial-e\not A]^2-m^2\rbrace\psi=\lbrace\left( i\partial-e A\right)^2 + \frac{1}{2i} \sigma^{\mu\nu}F_{\mu \nu}-m^2\rbrace\psi=0$$ And I need to find the form of the spin dependent term to get the final expression $$g...

Can we predict the positive parity, and zero spin of the Higgs boson from the decay mode: 𝐻 → 𝛾𝛾?

In Griffiths Elementary Particles (2nd, revised edition) there is a footnote on page 241, which states that the photon states with ##m_s = \pm 1## are related to the polarization vector by: $$\epsilon_+ = \frac 1 {\sqrt 2} (-1, -i, 0) \ \text{and} \ \epsilon_- = \frac 1 {\sqrt 2} (1, -i, 0)$$...

In the context of non relativistic quantum mechanics, or better, if I consider the neutrino's mass to be zero, the phrase seems to me puzzling. What I know is that if I know the direction of motion, I know the spin projection onto that direction, say ##\hat{z}##-direction. But to not violate...

I got confronted with this issue: Suppose we have Alice and Bob, each of them measuring the quantum spin on one of a pair of electrons along parallel axes, thus yielding an identical spin for both with each measurement. Now Alice's measurement is done earlier than Bob's. Can we now predict...

Let we have ##J_i \in{J_1,J_2,J_3}## ,and ##K_i \in{K_1,K_2,K_3}##, rotation and boost generators respectable . ##A_i=\cfrac{1}{2}(J_i+iK_i)##, and ##[A_i,A_j]=i\epsilon_{ijk}A_k## ##[K_i,K_j]=-i\epsilon_{ijk}J_k## ##[J_i,K_j]=-i\epsilon_{ijk}K_k## How proof that ##(m,n)A_i=J^{(m)}_i\otimes...

Hello, I have a question about a statement made on a YouTube physics lecture I was (am) working through chapter 4 section 4 (4.4) - “Spin” of Griffiths. (only because I own this book ) I found the YouTube lectures by searching for phrases like “quantum Griffiths online lectures”. One of the...

Hi all, I'm preparing a short presentation about the Kondo effect. I'm going to talk about the Anderson model and then Kondo's approach to deriving the logarithmic term using perturbation theory. Here's my question: why is it important that the spin of the impurity flips? I understand that...

In equation (3) of this article https://arxiv.org/pdf/astro-ph/0605418.pdf , on page 3, you can see an expression for the vacuum energy density of a field as a function of its particle spin, particle mass and the wave number k. It is fairly straight forward to derive the integral portion of...

During a SG experiment, the components N and S of the magnetic field are placed at the exact distance from the beam of particle?(or with precise approximation) What would happen if for example S is placed a little more distant from the beam of particle than N? Will we observe more deflection...

In the brilliant.org website talking about quantum properties it is said that neutrons coming from a nuclear oven and passing through two permanent magnets of opposite polarity hit a surface only at the top and the bottom of it (there is no continuity) because the spin property is quantized and...

Momentum ##\vec{p}## and position ##\vec{x}## are Fourier conjugates, as are energy ##E## and time ##t##. What is the Fourier conjugate of spin, i.e., intrinsic angular momentum? Angular position?

If thermal motion (collision of atoms) changes the direction of an atom, will that change the direction of spin? If so, how much time does it take from the change in the atom orientation to the change in the spin?

Hello! I am reading about spin-orbit coupling in Griffiths book, and at a point he shows an image (section 6.4.1) of the vectors L and S coupled together to give J (figure 6.10) and he says that L and S precess rapidly around J. I am not totally sure I understand this. I know that in the...

I've been looking hard (really, I have) for an explanation of what 'spin' is. Is there any way to explain this in a physical-real way, or is it 'just a thing'? Every description I have come across, and I mean dozens, say something like 'well, it's like angular momentum but it isn't really that...

Assuming we have a 3 phase motor I've always wondered why is it that the rotor spins rather than just being compleltly pulled towards the direction of the phase or the electromagnet? What causes that angular movement?

I am pretty confused where to even start with this question, which is not a good thing less than a week before the final :(. One thing in particular that I don't get is that I thought we were using the Clebsch-Gordon coefficients for ##\vert jm \rangle ## states, not for ##\vert J, J_z \rangle...

Hello there, I don't really get the difference between the extrinsic or intrinsic spin hall effect or contribution. As i understand, in extrinsic you have spin scattering by impurities, so its the spin orbit interaction of the spin with its orbit, and this orbit is influenced by an impurity...

$$H$$ can be rewritten as $$H=\frac{1}{2}(S^2-S_{1}^2-S_{2}^2-S_{3}^2-S_{4}^2)$$. Let's focus on the x component, $$J^x=\sum_{i}S_i^x$$. Now $$S_1^x$$ commutes with $$S^2_1, S^2_2, S^2_3, S^2_4$$, but does it commute with $$S^2$$? If not, what is the exact relation between $$S^2$$ and $$S_1^x$$?

I have tried doing the obvious thing and multiplied the vectors and matrices, but I don't see a way to rearrange my result to resemble the initial state again: ##(\mathcal{D_{1y}(\alpha)} \otimes \mathcal{D_{2y}(\alpha)} )|\text{singlet}\rangle = \frac{1}{\sqrt{2}}\left[ \begin{pmatrix}...

Would this be an accurate portrayal of measuring the spin of an electron with a SG detector?: The electron is in a superposition of spin-up and spin-down; Upon entering the magnetic field of the SG detector, the electron enters a superposition of an upward trajectory and a downward trajectory...

Hi, some time ago our professor told us (en passant) to evaluate this quantity: $$<F|n_m( \mathbf x) n_{m'}(\mathbf x) |F> - <F|n_m( \mathbf x)|F><F|n_{m'}(\mathbf x) |F>$$ And then he said: "you'll find that this quantity may not be zero. In particular when the electron are correlated it will...

For this problem, since the weight force on the "particle" (child) is not always aligned with the tangential circular path of the disks, I couldn't think of a way to use rotational kinematics equations. As such, I tried to solve the problem using work principles (namely, that the change in...

Why spin-matrixes and spinors have more rows for particles with greater spin (https://en.wikipedia.org/wiki/Spin_(physics)#Higher_spins)? As I understand every row is for 1 spin orientation, but why does number of possible orientations depend of magnitude of spin?

I want to understand this topic but I can not understand very well so please suggest any reading for good conceptual grasp of this topic.

For a tetrahedron with four spin (1/2) particles, I know there are three separate energy levels at $$l=2,l=1,and l=0$$. My question is how I would go about finding the degeneracy of each level. I know that the number of states must be $$2^4$$. Any clues on where to start would be appreciated...

Hello everybody, Im looking for a good explanation for the Rashba effect or Rashba Spin Orbit coupling (when it is the same effect with 2 names?) . If somebody can help me here that would be awesome. Moreover i try to understand the intrinsic mechanism of the Spin Hall Effect with the Berry...

Consider a qubit. Given a state equation, how to calculate the probability of finding spin in +x direction?

Okay i was reading abrikosov's book and he said since in QM spin only changes by integer values boson excitiation happens one at a time and fermion ALWAYS appears or disappears in pairs. but isn't change from a spin up to spin down 1/2 to -1/2? or i had the wrong convention which |1/2| shouldve...

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Hello, Im not sure if get the meaning of spin relaxation. In the case, if you have a spin polarized current, what happens there if you talk about spin relaxation? Is it just the phenomena that after some time the spins will pointing in all direction? If that is right why that happens?

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Addressing to electron as being rigid body that precesse is probably controversial. Are there any attempts to stick to that model and to calculate its quantize tangent velocity?

Hello everybody, Lets say we have an atom with an electron that have a spin. That spin can only pointing in 2 directions, in s_1=\hbar*1/2 and s_1=-\hbar*1/2 and therefore the magnetic moment of an electron is pointing on the opposite site. My Problem here is appearing when whe apply an...

Dear PF, As an excercise I am to find out how the expectation value of the spin operator evolves over time. There was a hint, stating that it is enough to show that $$ e^{i \frac{\phi ( \hat{n} \cdot \sigma )}{2}} \sigma_i e^{- i \frac{\phi ( \hat{n} \cdot \sigma )}{2}} = [R_{ \hat{n} }]_{ij}...

Hello all and thanks for viewing this, I am in need of some assistance to solve a problem to size an AC motor rotating this load (power transmission will be trough belt & pulley). I have a hollow cylinder (pipe) that needs to spin 25 RPM: - OD = 50 mm - ID = 48 mm - M = 200 kg - Total length...

What kind of research is currently going on in the field of quantum spin liquids and why do we study spin liquids?

Homework Statement: spin dephasing time Homework Equations: spin relaxation time Hello, i have seen the next equation that relates the spin dephasing time of an ensemble of électrons T2* with the spin relaxation of a single electron T2, and I would like to know how it was deduced/proposed...

Summary: If a measurement outcome depends on the measurement setup, is de measured not real or the measurement? If the factual outcome of an electron-spin measurement depends on the orientation of the SG magnet, for instance up or down in one orientation and left or right in the other, does...

Hello everybody! Let's begin with the spin. Spin of the ##\Lambda## is ##1/2## and of the pion is ##0##: $$ \frac{1}{2} \otimes 0 = \frac{1}{2}$$ Since I know from the homework statement that ##L=1##: $$ \textbf{J} = \textbf{spin} \otimes \textbf{L} = \frac{1}{2} \otimes 1 = \frac{1}{2} \oplus...

Please see this page and give me an advice. https://physics.stackexchange.com/questions/499269/simultanious-eigenstate-of-hubbard-hamiltonian-and-spin-operator-in-two-site-mod Known fact 1. If two operators ##A## and ##B## commute, ##[A,B]=0##, they have simultaneous eigenstates. That means...

Summary: What if the Earth would have spin around itself twice as it's speed? What would have be the consequences? How would has it affect the climate and living things?

Summary: please help me understand the following questions from Physics GRE test Thank you very much! To be honest i really hate this formalism. Memorizing such things is pain. but like everything it is what it is

In other words, does there exist, for an electron, a definite direction in physical space such that a measurement of its spin along that direction always give spin up, 100% of the time?

Why can't the general state, in the presence of coupling, take the form $$\psi_-(r)\chi_++\psi_+(r)\chi_-$$ where ##\psi_+(r)## and ##\psi_-(r)## are respectively the symmetric and anti-symmetric part of the wave function, and ##\chi_+## and ##\chi_-## are respectively the spinors representing...