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### Bra Ket Notation and Derivative [duplicate]

Let $$a$$ be the partial derivative symbol with respect to $x$. What is $$\langle x|a|x \rangle$$ equal to? I think it is 0 but not sure.
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### Transformation connecting two representations - Quantum mechanics [duplicate]

I am working on Dirac's paper The Lagrangian in Quantum Mechanics. He looks for the analogy between a classical transformation between two sets of coordinates and momenta $p_r$, $q_r$ and $P_r$, $Q_r$ ...
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If $\hat{p}$ acts on position eigenstate, it is $$\tag{1}\hat{p}\left|x\right\rangle=+i\hbar\frac{\partial }{\partial x}\left|x\right\rangle .$$ But in general $$\tag{2}\hat{p} = -i\hbar \frac{\... 2answers 409 views ### Quantum field theory for the gifted amateur: problem 2.4 I am trying to do problem 2.4 in the book "Quantum field theory for the gifted amateur". I have a math background but little training in physics. I am asked to use the identity$$\langle x \mid p \...
In the course of calculating $$\langle x|\hat{p}|\psi\rangle$$ I have a step which is: $$\langle x|\frac{\hbar}{i}\frac{d}{dx}|\psi\rangle=\frac{\hbar}{i}\frac{d}{dx}\langle x|\psi\rangle.$$ What is ...