Quasiparticles arise out of a collection of particles, that's why they're emergent
Maybe 'emergent' was the wrong word here. I meant that particles are convenient ways of describing behavior of the fields in many (but not all) cases, with the fields themselves considered to be the (more) fundamental description of reality.
Quantization exists and isn't just a convenience.
First of all, if you think of a photon as some small ball, not that's not what it is. Mathematically a photon is defined as a state of the EM field (which has been quantised into a set of harmonic oscillators called "normal modes") in which there is exactly one quantum of excitation of a specific normal mode (with given wavevector and frequency). Depending on which kind of modes you consider, a photon could be a gaussian beam, or even a plane wave, so not something localised like you would say of a particle.
Unlike photons, electrons have a position operator, so in principle you can measure and say where one electron is. The same is impossible for photons. Also electrons have a mass, but photon are massless. This means you can have motionless electrons, but this is impossible for photons: they always move at the speed of light. Electrons have a non-relativistic classical limit, while photon do not.
W. E. Lamb used to say that people should be required a license for the use of the word "photon", because it can be very misleading.
"Visualizing video at the speed of light — one trillion frames per second" (2012) https://youtube.com/watch?v=EtsXgODHMWk&
But is there an identity function for a photon(s), and is "time-polarization" necessary for defining an identity function for photons?
Since it lives and dies in the same instant, it can't have a position—because the moment it exists and the moment it doesn't is exactly the same time.
It takes time—even for light—to get from point A to point B. However, the measurement of any positions—relative to the photon itself—will always be the same. It's related to that property of quantum physics that allows two particles to exists in two different places at the same time.
> Think of it like this: From the perspective of the photon, it lives and dies in the same instant. Even if it traveled across the entire universe.
Would an appropriate analogy be a "glider" from Conway's Game of Life? "Lives and dies in the same instant" isn't exactly the same, but I'm thinking of how no parts of the glider move while the glider as a whole "moves" across the board.
Yeah I think generally "sextic" is the highest you see before people stop doing that, and that one's somewhat uncommon I'd say. ("Quintic" is actually fairly common, contrary to what I said earlier, oops.) The fact that seventh-degree would be "septic" might be one reason stop with the words at that point!
Annoyingly, people often use "exponential" colloquially to mean anything faster than linear, but in fact lots of things are faster than linear.
From the other responses, it sounds like "none of the above". It's more like a "polynomial curve" that is only sometimes quadratic. Is "polynomial curve" a thing? "Power curve" / "power function"?
Ok, it's different in that liquid flows through pipes and electrons flow through crystal lattices or whatever, so electrons go between and around the material while liquid is bounded by it.
It makes me speculate that electron flow through a metal is sort of like liquid flowing through a compressible boundary tube, whereas flow through a non-metal has rigid walls. Non-metals reject the electrons, metals allow them to play Spiderman and hitch a temporary ride (if you'll forgive the overly particle-centric analogy.)
If resistivity is determined by the equivalent of turbulence, though, I've no idea what the graph against temperature should be. Do electrons travel faster when there's less resistance?
> Ok, it's different in that liquid flows through pipes and electrons flow through crystal lattices or whatever, so electrons go between and around the material while liquid is bounded by it.
This is not perfect, but it works at a high level.
The main difference with e.g. water flows is that what restricts electron flux is traps. Electrons are not limited by walls that prevents them from going outside channels, instead they are held in place by atoms’ nuclei.
In a conductor, the “force” holding them is effectively zero, so when an electron comes in on one side, another one comes out of the other.
In a semiconductor. An electron needs some energy to get out of its trap before it can move. Then, “freed” electrons hop from trap to trap and the current is the overall effect of this. Electrons do not have to move far to create a current, there just needs to be enough of them. There is no real macroscopic analogy for this.
In an insulator, electrons just don’t get out of their traps because the energy required is too large.
This ignores a lot of details and quantum effects, but it is still a useful way to think about this.
> It makes me speculate that electron flow through a metal is sort of like liquid flowing through a compressible boundary tube, whereas flow through a non-metal has rigid walls.
Not really. Electrons moving in a metal are slowed down by a lot of different phenomena but this cannot really be considered as a compressible fluid. The effect is more similar to viscosity than compressibility.
In non-metals, electrons just don’t move unless they are made available, for example by doping or with a source of energy.
> Non-metals reject the electrons, metals allow them to play Spiderman and hitch a temporary ride
The general model is that metals let electrons flow and non-metals hold on to them.
> If resistivity is determined by the equivalent of turbulence, though, I've no idea what the graph against temperature should be. Do electrons travel faster when there's less resistance?
The analogy kind of breaks down here. There are competing effects and conductivity as a function of time is often highly non-trivial. In general, the number of electrons available increases with temperature, but scattering by other electrons, vibrations and defects also increases. Overall, resistivity tends to increase with temperature in metals and decrease in semiconductors, but there are exceptions.
Presumably electricity has something to do with positive charge at the back of the 'pipe' and negative charge at the 'front' (or have I got those backward?), perhaps a better visualization would be that they're all rolling down an inclined plane together?
Reminds me of the elephant and rope adage: young elephants are trained with small chains, which as they mature they outsized and could easily break but don't.
Though to give credit to researchers, those new experiments of "listening" for electron perturbations seem amazing. That's just a brilliant idea. Theorists often like to pretend they're better than the experimentalists, but without proper data the theorists get stuck in dead ends. ;)
Electron goes into one side, another electron shoot out from the other side.
It didn't went through, but acting like one. "quasi" particle maybe?
I have no idea what's going on, correct me if I am wrong
“The violation of the standard theory of solids in these strange metals is so dramatic—it’s in your face,” says Qimiao Si, a physicist at Rice University who collaborates with Paschen.
“There’s no question there’s new physics.”
baerrie•8mo ago