1. ### Why the Stern-Gerlach experiment didn't detect the L?

i recently read about the stern-gerlach experiment and found out that they did it in the first place to verify the principle of the "space quantization " introduced by Bohr , and they thought they did detect the quantization of the orbital angular momentum of ( L = 1 , m = 1,-1 ) neglecting the...
2. ### I What does an uncertainity of 0 mean?

I'm just starting my undergraduate Quantum Mechanics course. I had a homework problem to show that \Delta S_x = \sqrt{\langle S_x^2 \rangle - \langle S_x \rangle ^2} = 0 , S_x being the spin in the x direction. I managed to solve it, but the physical interpretation is confusing me. If I...
3. ### I Relation between spin and solar winds

I was thinking to myself, how come are particles coming from the sun gets deflected the way they do due to earth's magnetic field? They are getting pulled toward the poles, but if we think in terms of classical Lorentz force, they should not just follow the magnetic field lines, but rather start...
4. ### I Calculate a spin state as a function of the base spin states

Practically it is said that, given two spin states |u⟩ (up) and |d⟩ (down) - which are the spin measured along the +z and -z semiaxes - such that they are orthogonal ( ⟨u|d⟩ = ⟨d|u⟩ = 0), it is possible to write any other spin states using a linear combination of these two (because they are a...
5. ### I Clebsch–Gordan coefficients: An Identity

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
6. ### A Relation between Dirac's equation density matrix and current with spin

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...

12. ### B Confusion over spin measurements

I will refer to the spin example outlined in the opening chapters of the Theoretical minimum. Suppose we prepare a spin with a z component of +1. If we rotate the apparatus about 180 degrees, the ‘classical component’ of the prepared spin vector along the new axis of the detector is -1, so...
13. ### I Notation for vectors in tensor product space

Suppose I have a system of two (possibly interacting) spins of 1/2. Then the state of each separate spin can be written as a ##\mathbb{C}^2## vector, and the spin operators are made from Pauli matrices, for instance the matrices ##\sigma_z \otimes \hat{1}## and ##\hat{1} \otimes \sigma_z##...
14. ### I Do spin operators 'appear' to commute for an entangled spin state?

Let's consider Bohm's paradox (explaining as follows). A zero spin particle converts into two half-spin particles which move in the opposite directions. The parent particle had no angular momentum, so total spin of two particles is 0 implying they are in the singlet state. Suppose we measured Sz...
15. ### I How to know where the up and down spin go in the wavefunction?

We are given the wave function with spin, but it doesn't say in which Ylm each spin X± goes. So how do I know? Examples; (1) Ψ = 1/√3 R21(r) ( Y10 √2Y11 ) Here we have the up Spin X+ to Y10 and the X- to Y11 I notice the X- went to...
16. ### A Has the 2-stage Stern-Gerlach experiment been performed?

In http://www.feynmanlectures.caltech.edu/III_05.html#Ch5-S1, Feynman mentions that the 2-stage Stern-Gerlach experiment, which proves the electron spin states to be in a superposition, has never been actually done! I have also not seen any paper reporting such an experiment. My question is, has...

25. ### I Does a free electron have an orbital magnetic moment?

I know that total magnetic moment of an electron (I am not sure if it is magnetic moment of electron or atom, please clarify this) is sum of magnetic moment caused by orbital motion and spin angular momentum. So, Total magnetic moment = Orbital magnetic moment + spin magnetic moment Do I have...
26. ### I How Would Electron Entanglement Affect Photon Emission

Suppose you have a pair of electrons in the same quantum state, and are thus spin entangled, and they absorb a pair of photons and release them at the same time. How would this affect the photons? Would the photons be entangled? Would it affect the photon spin, and if so, how would it affect the...
27. ### I How can electrons have the same spin in triplet state?

Hello, I don't understand how can electrons in triplet state can have the same value of spin? Shouldn't the spins be different because two fermions can't have the same state? The following picture explain my question in more detail.
28. ### Is this really an excited state?

The figure below is from a textbook. It is explaining what excited states are using carbon as an example. I don't necessarily agree that the the state labeled as "example excited state 1" is really an excited state. Since the electrons in the 2p orbitals are unpaired, and in the absence of a...
29. ### I How to calculate each car tyre load during cornering?

This is about vehicle physics. I know how to calculate weight on each axle on a car during deceleration. Given the picture below: The weight on the front axle is calculated as: Wf=(c/L)*W-(h/L)*M*a and the weight on the rear axle is calculated as: Wr=(b/L)*W+(h/L)*M*a where c and b are the...
30. ### I Difference between parallel and antiparallel spins?

What is the difference between parallel and antiparallel spins for a pair of nucleons? My understanding is that nucleons have a strong tendency to pair - proton with proton, neutron with neutron, proton with neutron. When they pair their spins either: cancel (spins pair antiparallel) pairing...