3 ms·
If particles can be understood as resonances in a field then it’s hard for me to understand “stable” particles. What keeps them around? My mental model for reso
by m-atoms 5y ago
If particles can be understood as resonances in a field then it’s hard for me to understand “stable” particles. What keeps them around? My mental model for resonance and waves requires some kind of constant input energy to maintain the oscillations in the field which produce the particles. What am I missing?
- evanb 5y agoResonances are like vibrations on a trampoline; stable particles are more like lumps in a carpet. Usually what keeps particles stable is that they carry some quantum number(s) that is/are conserved, and no lighter combination of particles can be made with that combination.
- kurthr 5y agoThe observables are conserved, but I guess I always thought of the internal complex quantum states spinning away on their own.
- klyrs 5y agoSuperconductors can theoretically produce perpetual motion: once you set up a supercurrent, it will keep going forever. The caveat being that the electrons that are to move perpetually cannot do work of any kind*. That is, the field generated by the supercurrent cannot be interacted with. Likewise, an ideal LC circuit made of superconducting material can theoretically ring forever, provided "nobody hears the sound". So, given my understanding of the physics, nature does not forbid stable perpetual resonances (though engineering constraints may forbid even microscopic perpetual resonators). * When people talk about "perpetual motion machines" they tend to want to extract energy from them. That's folly.
- cout 5y agoIs that assuming that the superconductor itself does not undergo particle decay, or is there something special about superconductors that make them unusually stable compared to other matter in the universe?
- klyrs 5y agoYeah, I don't know jack about nuclear physics, so I drew an analogy to a field that I'm more comfortable reasoning about, the electromagnetic field.
- kurthr 5y agoPart of the difficulty in that analogy is that we normally think of things as damped by some surrounding media. For particles (modeled as field resonances storing quantized spatially concentrated energy) the only damping is coupling to other resonances (e.g. other particles). The particles were created by those interactions and they be annihilated (or decay) into other particles depending on how those resonances couple. Often due to quantization, this requires multiple particles including photons to "transmute" and that combination tends to reduce the likelihood of the interaction. That's my intuition from 30 years ago, anyway.
- m-atoms 5y agoThis was the most helpful for me, thanks!
- bsder 5y ago> My mental model for resonance and waves requires some kind of constant input energy to maintain the oscillations in the field which produce the particles. Your intuition is inverted from reality. Quantum mechanics dictates that a harmonic oscillator in a state will remain oscillating in that state indefinitely unless perturbed. This has the counterintuitive effect that an atom with an electron in an excited state will remain there indefinitely if you can cut off the atom from external interactions. This was, in fact, one of the arguments that Bohr used against Einstein. Experimentally--atoms decay--there is no denying that. However, Einstein's formulations said that atoms should not decay without external influence. It turns out--Einstein was right. However, those kinds experiments require things like laser traps that were far beyond the capabilities of the time.