# Tagged Questions

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### What does the notation $\Psi_k/(\Psi_k,\Psi_k)^{1/2}$ mean?

I am currently reading the paper "Gravitation and quantum mechanics for macroscopic objects" by F. Karolyhazy (1966). In his paper, he uses certain notation that I haven't come across before (he also ...
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### Using bra-ket notation?

Am I using Bra-ket notation correctly? I want to define a superposition of the states, $|0\rangle$ and $|1\rangle$. Is it simply? $|0\rangle + |1\rangle$ I can't find any non-technical information ...
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### Uncertainty Definition QM

On my introductory course in Quantum Mechanics, the uncertainty of an operator $A$ in the state $\psi$ is defined by $$(\Delta A)^2_{\psi}=\langle(A-\langle A \rangle_{\psi})^2\rangle _{\psi}$$ I'm ...
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### Writing an arbitrary operator in bra-ket notation

An annoying fact about my physics textbook (Griffiths' Introduction to Quantum Mechanics) is that it introduces bra-ket notation without telling us how to use it. So I have a two-part question for SE: ...
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### Basic question on bra-ket notation

Which of the following corresponds to a $\psi(x)$, a wavefunction written in the position basis: $x| \psi\rangle$ or $\langle x| \psi\rangle$? If it is the second expression (which my textbook ...
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### Vector $\vec{z}$ and its conjugate transpose $\overline{\vec{v}^\top}$ - is it the same as $\left|z\right\rangle$ and $\left\langle z \right|$

Lets say we have a complex vector $\vec{z} \!=\!(1\!+\!2i~~2\!+\!3i~~3\!+\!4i)^T$. Its scalar product $\vec{z}^T\!\! \cdot \vec{z}$ with itself will be a complex number, but if we conjugate the ...
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### Inner Product Spaces

I am trying to reconcile the definition of Inner Product Spaces that I encountered in Mathematics with the one I recently came across in Physics. In particular, if $(,)$ denotes an inner product in ...
If $i$ and $j$ are two variables then Kronecker delta is written as $$\delta_{i,j}~:=~\begin{cases}1 \hspace{3mm} \mbox{if} \hspace{3mm} i=j,\\ 0 \hspace{3mm}\mbox{if} \hspace{3mm}i \neq ... 1answer 946 views ### Wave function and Dirac bra-ket notation Would anyone be able to explain the difference, technically, between wave function notation for quantum systems e.g. \psi=\psi(x) and Dirac bra-ket vector notation? How do you get from one to the ... 2answers 350 views ### In Dirac notation, what do the subscripts represent? (Solution for particle in a box in mind) So the set of solutions for the particle in a box is given by$$\psi_n(x) = \sqrt{\frac{2}{L}}\sin(\frac{n\pi x}{L}). In Dirac notation $<\psi_i|\psi_j>=\delta_{ij}$ assuming $|\psi_i>$ ...
Let $H$ be a hilbert space and let $\hat{A}$ be a linear operator on $H$. My textbook states that $|\hat{A} \psi\rangle = \hat{A} |\psi\rangle$. My understanding of bra-kets is that $|\psi\rangle$ is ...