Questions tagged [angular-momentum]

The conserved quantity arising from a rotational invariance. Combine with rotational-dynamics for the classical mechanics approach and quantum-mechanics for the QM interpretation

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What happens when you shine circularly polarized light at a pole of a rotating black hole?

Circularly polarized light carries spin angular momentum (SpAM 😉), so shining it into a pole of a spinning black hole from a point on the rotation axis of the BH should raise the angular momentum of ...
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Prove $d/dt\langle L\rangle=\langle N\rangle$ without computing over a specific basis

In Griffith 3rd Edition, Problem 4.23 asks for the proof of $$\dfrac{d}{dt}\langle\mathbf{L}\rangle=\langle\mathbf{r}\times-\nabla V\rangle=\langle\mathbf{N}\rangle$$ One evaluates $[\mathbf{L},H]$ ...
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No net torque about principal axis

I’m trying to follow the proof for why no net torque is required to sustain constant rotation about a principal axis. I am confused by the proof by contradiction above. How does “rotating the axis and ...
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Connection between infinitesimal rotations and angular momentum (classical)

What is the connection between infinitesimal rotations and angular momentum, classically? I am not interest in any QM theory. How does one regard infinitesimal rotations as a generator of angular ...
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Confused about selection rules in optical transitions

This question is motivated by this paper in particular (let me know if it is not open access). They measure transitions between electronic levels inside an ion, placed inside a crystal. In Fig. 2, ...
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Electron spin in Pauling's General Chemistry book

I have a question regarding the interpretation in General Chemistry by Pauling (p. 77 - 78) about the spin of the electron/ it's angular momentum vector direction in a magnetic field: It was ...
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$\vec L$, $\vec S$ and $\vec J$ of the atom or electron when considering the Zeeman effect

I am confused regarding the different angular momenta considered when dealing with the Zeeman effect. I don't know whether the different angular momenta are attributed to the entire atom, exposed to ...
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Limit of angular momentum and "alone" black hole singularity

I just read in a book that a black hole has an angular limit at which the event horizon would disappear, leaving the singularity alone. This question is not about this said statement — even though I ...
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Equations for rotational motion for fluids [duplicate]

For a solid particle, we write $\mathbf{F} = m\mathbf{a}$ and $\mathbf{T} = I \mathbf{\alpha}$ to account for linear and angular momentum balance. As far as I know, these two momentum conservation ...
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Is a black hole spherical?

Black holes are usually created when massive stars use up all their fuel and collapse due to gravitational collapse. All stars rotate. However, since angular momentum must be conserved even when they ...
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Do all the planets orbiting a star lie in one plane? [duplicate]

If you look at our solar system and our galaxy, the stars and planets are generally all in one plane. So, are all galaxies in one plane? And why are they in one plane?
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Translational motion of a rigid body and summing angular momenta

I'm trying to understand the most accurate way to determine the angular momentum of a rigid body that is undergoing translational motion around a point. Perhaps I missed something in my classical ...
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Why does it make sense to say that "full shells" have 0 angular momentum even when not using the configuration model?

When talking about the periodic table, one is often confronted with the notion of a 'configuration of electrons', i.e. we have the configuration $1s^22s^22p^2$ for carbon for example. This notion ...
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What are physical laws behind the vibrational energy transfer?

My orbital sander causes objects sitting on the surface where the force is applied to levitate slightly and rotate in the opposite direction to the spin of the sander. The harder I push down on the ...
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Can a hypothetically massless object/particle of finite size spin around its own center in a fixed position in space? [closed]

Imagine a hypothetically spinning massless object or particle of finite size. I am not referring to orbital spin but spinning around its own center like a flywheel spinning with a fixed center. This ...
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Electric and magnetic field lines in a plane wave of finite extent

In an infinite plane wave propagating in the $z$ direction, the momentum density is $\mathbf{p}=(4π)^{-1}(\mathbf{E} × \mathbf{B})$ which points in the $z$ direction; therefore, the angular momentum ...
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Exact meaning of the mass $M$ in the Kerr metric event horizon?

Posting this as I have so far not been able to find a straightforward answer to the following question. The formula for the outer event horizon of a kerr black hole is given by the following equation: ...
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Frame dragging caused by a stream of particles with aligned spins

In theory, does an elementary particle, with intrinsic spin, induce an immeasurably tiny amount of rotational frame-dragging, i.e. can quantum spin cause a Lense-Thirring effect? There is the Einstein-...
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