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| bio | website | |
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| age | ||
| visits | member for | 1 year, 3 months |
| seen | 19 hours ago | |
| stats | profile views | 1,575 |
I like physics.
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20h |
revised |
Quantum mechanics and everyday nature Typo |
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20h |
revised |
Quantum mechanics and everyday nature Major edit for clarity and typos, with some added material on electron delocalization |
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2d |
answered | Quantum mechanics and everyday nature |
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May 19 |
awarded | Guru |
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May 14 |
answered | Why Planck scale is so important? |
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May 5 |
awarded | Nice Answer |
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Apr 27 |
awarded | Nice Answer |
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Apr 22 |
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Does entanglement not immediately contradict the theory of special relativity? @BrandonEnright, weighing in a bit late, this answer I provided to another question addresses (without using math) how you can get correlations without at the same time transmitting information. |
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Apr 21 |
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Why do ice cubes come out easier from top trays? That's actually the most straightforward solution I've seen yet! PAM-cubes! |
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Apr 19 |
awarded | Popular Question |
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Apr 3 |
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Are information conservation and energy conservation related? It's not mathematically proven, if that is your question. When I said "Conservation of mass-energy is an extremely well-defined and exhaustively proven concept," I was referring to a very rich and now centuries-old set of accepted literature and results that indicate you don't just get energy for nothing, nor can you get rid of it. The equation $E^2 = p^2c^2 + m^2c^4$ (the classic $E=mc^2$ is a simplification of that for unmoving mass) cleaned up the rule a bit, but did not change the rigidity with which the total conservation of energy, mass, and momentum is observed experimentally. |
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Mar 28 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? +1 for a really nice pair of belt videos, despite my very sincere "please no!" plea on that point :). "Exchanging buckles twice = 720$^{\circ}$" is going to confuse folks who see only a 360$^{\circ}$ rotation, but Feynman and others do explain why that is. Spin 1 becomes "no belts, just buckles", which alas is not mentioned in the description. The shared underlying math is correctly noted. But alas: I'm guessing that most folks who see even a good video like that will go away wondering why belts are "just like spin 1/2" (spinors) and buckles "just like spin 1". So: Good Feynman capture. |
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Mar 26 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? @JKL, oops, by "gives" I did not mean pair creation, which can produce anything with enough energy. From this Wikipedia article there is this line: "In other words, the spin-statistics theorem states that integer spin particles are bosons, while half-integer spin particles are fermions." The values are more than just labels of course, since spin 1 is the smallest possible unit of quantized angular momentum. That's why folks were more than a tad surprised when (via Stern-Gerlach I think) they found some particles to have half-unit spins. |
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Mar 26 |
awarded | Talkative |
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Mar 25 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? @JKL, great points. The math is well understood and leads neatly to the two types of statistics. So, if from that math you can show clearly why 1/2 spin offsets always give fermions and whole spins always give bosons, you may have the start of the kind of answer for which Feynman always hoped. |
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Mar 25 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? Hi @TMS: That would be "why are the two always correlated?" Bosons, with wavefunctions that are symmetric under exchange, always seem to have whole-unit spin; while fermions, with wavefunctions that are anti-symmetric under exchange, always seem to have spins that are offset by one half of a spin unit. It's that correlation that's a bit tough to explain in a simple way. I think it would also be fair to say that since there is no simple explanation even for what spin is at the level of an electron, which is after all a point-like particle, it's even tougher to explain its impact. |
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Mar 24 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? @gns-ank, thanks, I didn't know it was available online! |
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Mar 24 |
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Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? typo |
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Mar 24 |
asked | Did the Feynman heuristic of “simple effects have simple causes” fail for spin statistics? |
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Mar 24 |
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Why is there a linear relationship between charge and isospin? Thank you, actually. Your question prompted me to take a much closer look at this issue, which I've found curious for a long time. The use of symmetry groups to drive the definition and use of metrics is a very reasonable first-level heuristic, but I think it's also important to keep the link between the starting point and the results clearly in mind. Isospin started as a deep insight, one into a symmetry for which the relevant particles would not even be known for decades. Alas, it faded and ultimately became unusable for deep symmetries when it was locked into up-down quarks. Fascinating! |
