In this site: http://farside.ph.utexas.edu/teaching/qm/lectures/node23.html , how does one go from steps 141, 142 to 143? Shouldn't the result in 143 be [tex]A_{new} = e^{i \gamma} A_{old} e^{i \gamma}[/tex] ? Also, how does step 144 work (the entire thing from left to right?)(adsbygoogle = window.adsbygoogle || []).push({});

For step 144, here's how I see it (assuming step 143 is correct):

[tex]e^{-i \gamma} \frac{d}{dx} e^{i \gamma} = i e^{-i \gamma} \frac{d \gamma}{dx} e^{i \gamma} = i e^{-i \gamma} e^{i \gamma} \frac{d \gamma}{dx} = i \frac{d \gamma}{dx}[/tex]

in other words, I don't see how the extra [tex]d/dx[/tex] term popped up. Also, is my above work correct? I effectively stated that [tex]d\gamma/dx[/tex] and [tex]e^{i \gamma}[/tex] commuted as operators since they're both functions of [tex]x[/tex].

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# Operator and Commutor Question

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