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1:33 AM
Q: What is wrong with Weyl-Wigner representation?

Mauro GilibertiThe Weyl-Wigner representation is a useful tool to study QM from a semiclassical, phase-space point of view. My question is simple: if this method is so close to classical mechanics, why don't we use it for the whole theory of QM? Why do we need Hilbert spaces?

7 hours later…
8:28 AM
Q: 8.9875517923(14) means what?

James AdrianThe number $8.9875517923(14)$ appears in Coulomb's constant. I have read that it has something to do with the uncertainty of the accuracy of the number but answers have been unclear. Can somebody define the meaning of such notation?

4 hours later…
12:32 PM
Q: Why do higher harmonics have a lower amplitude than fundamental frequency

Rahul RWhen we pluck a string, it vibrates in all possible modes of vibrations. The lowest frequency possible is fundamental frequency and it is the most significant part of sound. But why do amplitude of higher harmonics decreases? Which formula is responsible? Also how is the energy of wave distribute...

8 hours later…
8:40 PM
Q: Difference between Free Fall and Constant Velocity

KiwiKiwiWe know that astronauts in the ISS feel "weightless" because they are in a perpetual free fall. The earth's gravity is the only force acting upon them, and it is accelerating them towards the earth's center at the same rate as the ISS. However, now imagine a crew in a spaceship very far from any ...

3 hours later…
11:30 PM
Q: Conservation of momentum and energy

Physicist0007In my physics book (chapter 9 - center of mass, linear momentum and collision), it is written Momentum should not be confused with energy. In some cases momentum is conserved but energy is definitely not. This is a bit confusing. So I want an example of a system where momentum is conserved but ...

11:55 PM
Q: Does data compression require energy?

JacksonSuppose I have a $C=1TB$ hard drive $H$, filled to the brim with English text. I'd like to compress this. Suppose the hard drive consists (abstractly) of zeros and ones, and that the number of ones in the initial state is $n_1$, so that the number of zeros is $n_0=C-n_1$. In practice, the zeros a...


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