6 votes

Why does spin acting along $x$ on the spin up state yield spin down?

...What I'm stuggling to understand is why applying $\hat{S}_{x}$ to $\ | \alpha \rangle \ $ yields $\ | \beta \rangle \ $ from an intuitive perspective beyond just plugging in the for $\hat{S}_{x}$ ...
hft's user avatar
  • 17.5k
4 votes

Stern–Gerlach experiment - what's so strange?

When a magnetic dipole is deflected by the magnetic field it releases the potential energy as light as it comes to rest. We measure the amount of deflection and therefore the initial orientation of ...
Er Jio's user avatar
  • 715
2 votes

Confusion about irreps of $SU(N)$: is the "color charge" the same as spin 1?

It is true that, given a $(2s+1)\times (2s+1)$ matrix representation of $S_x,S_y,S_z$, then $e^{i\theta \hat n\cdot\vec S}$ will be a $(2s+1)$-dimensional unitary matrix and thus in $SU(2s+1)$, but ...
ZeroTheHero's user avatar
2 votes

Stress-energy tensor spin-1 coupling

If you couple a field to the stress energy tensor in the Lagrangian, then you modify the stress energy tensor. For example, in linearized gravity, the Lagrangian contains a coupling $h_{\mu\nu} T^{\mu\...
Andrew's user avatar
  • 46.4k
2 votes

Decomposing direct product of spin-$s$ representation into direct sum

Here is the highest-weight idea: Consider a $2j+1$ representation of $su(2)$ with states $|j,m\rangle_1$, along with another $2s+1$ representation $|s,m'\rangle_2$, consider $$|j\rangle_1 |s\rangle_2 =...
bolbteppa's user avatar
  • 3,930
2 votes

Confusion about spin in 1 dimension

As you point out, there is no rotation group in 1 dimension. Spin must obey the same Lie algebra/group as angular momentum. You cannot have it in a dimensionality that cannot support the other. So ...
Cosmas Zachos's user avatar
2 votes

Do protons and electrons actually precess?

Existing answers seem a bit unclear to me, so here goes... Yes, they do precess. The easiest way to see this is in the average properties (also called expectation value). You can define a vector $\bf \...
Andrew Steane's user avatar
1 vote

Does the electromagnetic field "spin"?

An electromagnetic field has no charge or current and cannot ct as the source of another electromagnetic field. Hence, an electric field can never generate a magnetic field. What Faraday's law means ...
my2cts's user avatar
  • 22.8k
1 vote

Why is the Higgs boson spin 0?

I would like to add to these above answers another non-rigourous way, if one had forgotten, to remember that the Higgs boson has spin 0, through elimination. In 2012, it was directly observed that the ...
GerardoLo's user avatar

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