4 ms·
I know you're being sarcastic, but this is actually just table-stakes for any sort of research in fundamental physics. This is quite analogous to linear moment
by wnoise 4y ago
I know you're being sarcastic, but this is actually just table-stakes for any sort of research in fundamental physics. This is quite analogous to linear momentum being the generator of translation, yet having mysterious components in E&M that aren't a particle moving, but charge interacting with the somewhat inscrutable "vector potential".
- jojobas 4y agoMagnetic vector potential is actually directly measurable with a somewhat esoteric experimental setup.
- deleted 4y ago[deleted]
- Elpis1 4y agoIt's not quite measurable; the magnetic potential is gauge invariant, which means, among a great deal many other things, that it has no well-defined measurable value. However, it is certainly physical; things like the Aharonov–Bohm effect prove that.
- wnoise 4y agoYou're missing a "not".
- Elpis1 4y agoWhere?
- wnoise 4y agoin "the magnetic potential is gauge invariant". It differs for different gauges, so is not gauge-invariant, but gauge-dependent. A choice of A _is_ a choice of gauge. The theory using it (i.e. E&M Lagrangian) is what is gauge-invariant. This is a hyper-correction; in practice physicists apply the term in places adjacent to where it should be all the time.
- Elpis1 4y agoAh, sorry about that! You're right, of course; my brain slipped a bit.
- deleted 4y ago[deleted]
- mikewarot 4y agoYes, I'd like to own a few SQUIDs to play with. I've got some old Tesla patent drawings (bifilar coils) I'd like to understand better.
- aether-regained 4y agoIs this what you are referring to?: FLP-II-15–5 The vector potential and quantum mechanics https://www.feynmanlectures.caltech.edu/II_15.html#Ch15-S5 https://www.feynmanlectures.caltech.edu/II_15.html#Ch15-S5 " Precisely this experiment has recently been done. It is a very, very difficult experiment. Because the wavelength of the electrons is so small, the apparatus must be on a tiny scale to observe the interference. The slits must be very close together, and that means that one needs an exceedingly small solenoid. It turns out that in certain circumstances, iron crystals will grow in the form of very long, microscopically thin filaments called whiskers. When these iron whiskers are magnetized they are like a tiny solenoid, and there is no field outside except near the ends. The electron interference experiment was done with such a whisker between two slits, and the predicted displacement in the pattern of electrons was observed. In our sense then, the A-field is “real.” You may say: “But there was a magnetic field.” There was, but remember our original idea—that a field is “real” if it is what must be specified at the position of the particle in order to get the motion. The B-field in the whisker acts at a distance. If we want to describe its influence not as action-at-a-distance, we must use the vector potential. "
- lumost 4y agoFor a particular set of formalisms which some may find esoteric. It’s not wrong to wonder if the above is a true, but ultimately I insightful statement.
- saghm 4y ago> This is quite analogous to linear momentum being the generator of translation, yet having mysterious components in E&M that aren't a particle moving, but charge interacting with the somewhat inscrutable "vector potential" As someone who mostly just coasted in my two required physics courses in college and had no interest to study it further, this isn't really _that_ much more "obviously correct" to me than the first quote about angular momentum. Having never heard the term "generator of translation" or anything like it before, I wouldn't have been able to tell if was a rigorous, well-defined term or made up pseudoscience buzzwords before reading this thread.