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# Questions tagged [notation]

This tag is for questions on the meaning, history, and usage of various symbols and notation that are used to denote different quantities in physics. Don't forget to mention the reference, where you encountered those notations.

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### Justifications for the index upper lower labels in tensor component transformations

A (1,0)-type tensor may be written as $$V = V^{\mu} e_{\mu}$$ The component transforms as $$V^{\nu} = A^{\nu}{}_{\mu^\prime} V^{\mu^\prime}$$ (the basis can transform similarly) My question is, ...
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Very quick and short clarification: Knowing $R_{abcd} = - R_{bacd}$, is this symmetry true for for a,b components (i.e $R_{acbd}=-R_{bcad}$) or for the first two 'slots' of the tensor (i.e $R_{acbd}=-... 2 votes 2 answers 89 views ### Reordering Terms in Abstract Index Notation — General Relativity In General Relativity by Wald, the author makes a claim that I am trying to understand. The crux of my question comes down to understanding why$\eqref{eq1}$is true, but I have included the context ... 2 votes 0 answers 110 views ### Marginalisation of a joint probability distribution in bra-ket notation Given a wave function$\Psi(\vec r_1, \vec r_2)$, where$\vec r_1$and$\vec r_2$are the positions of particle 1 and 2, respectively, the probability of finding particle 1 at position$\vec r$(... 1 vote 3 answers 239 views ### Is it possible to solve cross products using Einstein notation? I'm considering a case where I have an equation of the form$\mathbf{x}\times\mathbf{b}+\mathbf{c}=0$; I wish to solve for$\mathbf{x}$given that$\mathbf{b}\perp \mathbf{c}$. It was in the context ... 0 votes 2 answers 58 views ### Grounding in Circuits [closed] The question is to find the current through the 8 Ω resistor. My textbook says that it is 3A as there is 0 potential at points "a" and "b" and thus it must drop by 24 V across the ... 1 vote 1 answer 73 views ### Nuclear physics notation This is probably a very basic question about notation. If we have the following notation for Boron nuclei: $$^{12}_5 B(1^+)\;\text{or}\; ^{10}_3B(3^+)$$ What does the number in the parentheses mean? I ... 1 vote 2 answers 240 views ### What does Griffith mean by adding a prime on integration variables? In the book "Introduction to Electrodynamics" by Griffith, the author mentions electric potential as a point function writes the equation for electric potential as Then in a side note he ... 0 votes 1 answer 60 views ### What does$p$mean in the energy-momentum relation? Suppose I have several particles each with some momentum vector$\mathbf{\vec p}_i$, what is$p$in the relation $$E^2 = E_0^2 + (pc)^2$$ Is it the magnitude of the vector sum of all$\mathbf{\vec p}...
Researching Cotton tensor I found in Wikipedia (https://en.wikipedia.org/wiki/Cotton_tensor): $$\tilde{C}=C+\text{grad }\omega\lrcorner W$$ with a comment "where the gradient is plugged into the ...
I'm watching MIT 8.06 Quantum physics, lecture $23.2$ See for example  Particularly See $5:41$. It is shown that P_{21}B(1)P^\dagger_{21}|u_i\rangle_1\otimes |u_j\rangle_2=|u_i\rangle_1\otimes |...