I was trying to follow http://www.youtube.com/watch?v=dCua1R9VIiQ&p=EFD655A9E0B979B7&playnext=1&index=54" lecture at the 4:15 mark but am having a little difficulty. In particular, why doesn't he have to take the commutator of all four of the terms you get when you square (p-eA).(adsbygoogle = window.adsbygoogle || []).push({});

Is he using :

[tex]\partial[/tex]q/[tex]\partial[/tex]t = [tex]\partial[/tex]H/[tex]\partial[/tex]pand the chain rule? If so, why doesn't he differentiate what's inside the parantheses of the Hamiltonian?

-Nate

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# Applying Heisenberg Picture Confusion

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