Physics Asked on May 10, 2021
The equation for the unitary evolution of an operator $hat{A}$ is given (as far as I understand) as $$frac{partialhat{A}}{partial t}=frac{i}{hbar}[hat{H},hat{A}].quadmbox(1)$$
It seems that $(1)$ is related to the Baker-Campbell-Haussdorf via a lemma which is written as follows: $$mbox{Ad}_{e^X}Y=e^{mbox{ad}_X}Y=e^XYe^{-X}=Y+[X,Y]+frac{1}{2!}[X,[X,Y]]+frac{1}{3!}[[X,[X,[X,Y]]]+…quad (2)$$
I notice that e.g. $$frac{partial}{partial lambda}big(e^{lambda hat{H}}hat{A}e^{-lambda hat{H}}big)bigg|_{lambda=0}=[hat{H},hat{A}].$$
This makes $(1)$ look like an infinitesimal change in $t$ on the left-hand side, and some sort of infinitesimal Lie group action of $hat{H}$ on the right.
Is this interpretation correct?
Any explanations, especially good texts to consult, would be greatly appreciated.
Thanks in advance!
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