- #1
Robben
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Homework Statement
Let ##|\psi\rangle \to |\psi'\rangle = \hat{T}(\delta x)|\psi\rangle## for infinitesimal ##\delta x##. Show that ##\langle x \rangle = \langle x \rangle + \delta x## and ##\langle p_x \rangle = \langle p_x\rangle.##
Homework Equations
##\hat{T}(\delta x) = e^{-i\hat{p}_x\delta x/\hbar}##
The Attempt at a Solution
I am confused. Why would ##\langle x \rangle = \langle x \rangle + \delta x##?
Shouldn't it equal ##\langle x \rangle?##
Since, ##\langle x\rangle = \langle \psi'|\hat{x}|\psi'\rangle = \langle \psi'|x\hat{T}(\delta x)|\psi\rangle = \langle \psi |\hat{T}^{\dagger}(\delta x)\hat{T}(\delta x)x|\psi\rangle = \langle x\rangle.##
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