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11 votes
3 answers

A rigorous derivation of Hund's rules

I was really looking forward to the atomic physics portion of my quantum mechanics class and was pretty disappointed with Griffith's hand-wavey qualitative description that was scarcely above the ...
Dutonic's user avatar
  • 727
3 votes
1 answer

How does the Hong-Ou-Mandel (HOM) effect conserve photon momentum?

HOM is a two-photon interference effect where temporally overlapped identical photons coming perpendicular to a beam splitter must leave it in the same direction. How is momentum conserved in this ...
Dan Barzilay's user avatar
2 votes
8 answers

Why does a higher frequency mechanical wave have more energy?

(that question may sound like my last question What makes a higher frequency sound wave more energetic? but I wouldn't consider it a duplicate, the focus is very different.) Comparing two mechanical ...
iwab's user avatar
  • 125
3 votes
1 answer

Landau&Lifshitz's derivation of the law of entropy increase - clarification

In Landau&Lifshitz V: Statistical Physics the following derivation of the law of increase of entropy is given. I need help understanding several crucial steps; I'll briefly summarize the notations ...
pppqqq's user avatar
  • 4,494
5 votes
1 answer

A limit of a particular Quantum Fidelity

I have the following problem. Let $\mathbf{\hat{\rho}}(t)$ and $\mathbf{\hat{\sigma}}(t)$ be two trace class positive operators acting on a Hilbert space of infinite dimension for all $t > 0$. More ...
Hldngpk's user avatar
  • 68