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Mar
13
comment A tensor summation question
Yes. Flat 3D space is usually called 'Euclidean.'
Mar
12
revised A tensor summation question
added 297 characters in body
Mar
12
answered A tensor summation question
Mar
12
comment A tensor summation question
But it's only unambiguous when the metric is Euclidean, so getting into the habit of writing everything with lower indices is a bad idea. It also looks sloppier.
Mar
12
comment A tensor summation question
Because using upper indices represent vectors while lower indices represent covectors. They are functionals of each other. Using all lower indices is ambiguous because you can't tell which is which.
Mar
12
comment A tensor summation question
You're using rather confusing notation. Are you summing over i and j? The repeated lower indices are pretty ambiguous.
Mar
11
awarded  Enthusiast
Mar
9
comment electrical forces of two charges repelling each other
Newton's Third Law.
Mar
8
answered A treatment of basic Kaluza-Klein theory
Mar
8
answered A thought on definition of momentum
Mar
7
revised Choosing the right point when calculating moments
deleted 72 characters in body
Mar
7
answered Choosing the right point when calculating moments
Mar
7
answered how quantum-mechanical particles react in the potential?
Mar
6
comment Are quantum mechanics and determinism actually irreconcilable?
My advice would be "don't tell the nature how it should behave." The universe doesn't have to conform to our naive philosophical biases. I tend to show people the following video when questions like these come up: youtube.com/watch?v=iMDTcMD6pOw .
Mar
6
answered Why geometrically four acceleration is a curvature vector of a world line? And what is proper acceleration?
Mar
6
awarded  Critic
Mar
5
comment Is energy always proportional to frequency?
The difference is the immense scale difference. Each particle in the cat has an attributed de Broglie wavelength, but since Planck's constant is so tiny these waves are very very small compared to the total size of the cat.
Mar
5
comment Is energy always proportional to frequency?
I'm not really sure what the question is. First of all, frequency of what? As for energy that isn't proportional to frequency, how about potential energy?
Mar
4
comment Gravitational Redshift around a Schwarzschild Black Hole
You're using Schwarzschild coordinates. In this coordinates $r$ does not correspond to radial distances. Physical distance which you would measure with a ruler correspond to an integral over $ds$. 99% of all confusion in GR comes from taking coordinates too seriously.
Mar
4
comment Gravitational Redshift around a Schwarzschild Black Hole
You're using Schwarzschild coordinates,