Physics Questions, Problems & Solutions : TransWikia.com ~ Page 816

Lorentz transformation of the Dirac function

Consider a Lorentz transformation that takes the $(x, y, z, t)$ coordinates of a point in Minkowski space into $(x', y', z', t')$. An electrically charged object at...

Asked on 10/10/2020 by Calin Galeriu

1 answer

Derivative in cylindrical coordinates

Why do we multiply a $frac{1}{r}$ factor for the gradient unit vector in $vec{theta}$ direction? and how is the angle a vector here?...

Asked on 10/09/2020

3 answer

Resistor circuit that isn't parallel or series

What's the equivalent resistance in this circuit (between points A and B)?...

Asked on 10/09/2020 by Carl Brannen

6 answer

Are irreversibility and unpredictability in a system caused by the huge number of molecules?

In my understanding, if we imagine two molecules in a system, we can predict what's going to happen and it's easier to reverse the process than to predict the motions...

Asked on 10/09/2020

0 answer

A form of entropy for pure states?

A previous question that I asked made me realize I had some major misconceptions about entropy. If I now understand this correctly, given the density matrix of a system,...

Asked on 10/09/2020 by Jlee523

1 answer

Absolute value of Jacobian when converting tensor density

I am currently reading Sean M. Carroll’s book about General Relativity. He claims that, in order to convert a tensor density of weight $w$ into a true tensor, one...

Asked on 10/08/2020 by Leon231000

1 answer

Setting a laser cutter focus in the meters range

Apologies if this is the wrong Stackexchange. All the laser-cutting searches led to graphicdesign.stackexchange.com. ?!?!?!? I have access to a laser cutting rig, a 200W CO2 beast, that needs...

Asked on 10/08/2020 by Sniggerfardimungus

1 answer

What is the formal definition of Coupling efficiency

Does anyone knows the formal definition of Coupling efficiency?I have been reading the term in photonics devices and optics. I have been searching for it, but I could not...

Asked on 10/08/2020 by Who

1 answer

Modeling a cut-off spherical wave in an imaging system

I need to model a "cut-off" spherical EM wave to carry on some energy calculations for an imaging system. Referring to the figure below, let's assume that we have a...

Asked on 10/08/2020 by Arrigo

0 answer

Matrix representation of trivial Hamiltonian

I was reading Kitaev 2009 periodic table paper when I came across the following "Let us define the trivial hamiltonian:"$$hat{H}_{text {triv }}=sum_{j}left(hat{a}_{j}^{dagger} hat{a}_{j}-frac{1}{2}right)=hat{H}_{Q}$$where$$...

Asked on 10/08/2020 by Jiahao Fan

1 answer

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