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In studying the Dirac equation, I often come across the unit momentum operator $hat{textbf{p}}$ which is defined as $$hat{textbf{p}} ={textbf{p} over |textbf{p}|},$$where $textbf{p}$ is supposedly the three-momentum...
Asked on 03/03/2021
2 answerWhy does a tower of building blocks (cubes) fall? Theoretically, as long as the center-of-mass is above the blocks' bottom faces, and as long as one does not shake the...
Asked on 03/03/2021
3 answerA pure state can be locally transformed unitarily to its Schmidt basis given by $$|psirangle_{AB} = sum_i alpha_i |irangle_A otimes |irangle_B$$ where $A$ and $B$ are both...
Asked on 03/03/2021
0 answerThe interior volumen of a typical black hole is greater than the one we expect when measuring its external area and calculating its volume: https://plus.maths.org/content/dont-judge-black-hole-its-area-2 But Wheeler's...
Asked on 03/03/2021
2 answerSuppose we need to convert $18text{ km/h}$ speed into $text{m/s}$. The answer is $5text{ m/s}$. But $5text{ m/s}$ has only one significant figure only whereas the...
Asked on 03/03/2021 by Arun Arora
1 answerI edited the question since this comment was (rightly) made:There are few things that are more annoying than questions where the question text is not self-contained.So:Quantum supremacy has been...
Asked on 03/03/2021
3 answerIn Condensed Matter Field Theory (page 288) by Altland and Simons, there is one mathematical formula: begin{equation}sum_mathbf{p} left(mathbf{p}boldsymbol{cdot}mathbf{v}right)left(mathbf{p}boldsymbol{cdot}mathbf{v}'right)Fleft(mathbf{p}^2right)boldsymbol{=}dfrac{mathbf{v}boldsymbol{cdot}mathbf{v}'}{d}sum_mathbf{p}:mathbf{p}^2Fleft(mathbf{p}^2right)tag{01}label{01}end{equation} Here, $mathbf{p}$ is the momentum, and ...
Asked on 03/03/2021
1 answerQuestionSo I read this interesting link:The most glaring problem is that the state spaces of classical andquantum mechanics are completely different, so you can’t have a...
Asked on 03/03/2021
1 answerIs it possible to extract real physical values from multiphase Lattice Boltzmann method simulation with Shan-Chen force? SC force is of the form $$vec{F^{SC}} = -psi(vec{x}) G sum_i w_i...
Asked on 03/03/2021
0 answerLet us assume that all we know till now is that two types of charges exist. One of them is possessed by an elementary particle called an electron and the...
Asked on 03/03/2021
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