“Trapping electrons in a crystal” is such a nonsensical way of conveying the idea of a flat band. Most isolated crystals trap all the electrons they have inside of them, or else the world will be full of free roaming electrons!

current carrying wire of finite length

Well I suppose a cheesy way of putting this is that there is no such thing as a “current carrying wire of finite length”, by itself.

To expand, just because one can calculate the contribution to the magnetic field at some spatial point from such an object, doesn’t mean it is the sole source of the field in a theoretically consistent manner. If you complete the “loop” with two semi-infinite horizontal wires, and another vertical wire at infinity (assuming it has an emf there to power the circuit), then the field will change due to the two horizontal wires. This construction however breaks rotational symmetry around the original wire (so you’ll not be able to compute the loop integral simply as B times circumference), and in order to restore that, instead of just two horizontal wires, you’ll have to have infinite such pairs in all radial directions (like a squeezed coaxial cable). Anyway, I guess the point is after “completing the circuit”, the “paradox” will no longer be there.

The Ying Yang is the “shape” of the light source. The point is that their technique can be used to infer the shape of an unknown light source, among other things. In so far as the data being recorded in the experiment involves two photons (or really, many identically prepared copies of two photons over time) and therefore 4 spatial dimensions (x y for each), then yes the 2d image they show is necessarily “interpreted” from the 4d “raw image”. Exposure time is 1min according to the paper, so not quite “real time”, but the whole theory is time independent (no time in any equation), so I imagine it can be shortened with e.g. higher laser power.

caveat: not an optics person so grain of salt…

The bigger black and white on the left is the “double exposure” of both the reference state and the unknown state and is observed. But the Yin Yang you see is the shape of the pump beam, which is the smaller black and white inset on the left. The colored one on the right is the reconstructed unknown state (that is, it is computed from b&w one and the reference state (not shown))

Appreciate the uplifting spirit, but not sure who this list is for. Physics undergrad? Talk to a professor. In grad school? Probably already has some personal taste and knows how to pick books that best suit one’s own style and need (plus talk to your peer/professor). Budding enthusiast? Pick a topic of interest and go from there – life is short, no need to waste time on every standard text book.

Also, quite a negligence not mentioning a single book from Landau & Lifshitz.

To be fair, time crystal is a real – albeit somewhat clickbaity – concept in physics, proposed by none other than the Nobel laureate Wilczek. In simple terms, a time crystal is something whose frequency is not a harmonic of what’s driving it (e.g., its periodicity could be double that of the drive). It’s a “crystal” because it’s breaking the (temporal) symmetry of the governing theory, just as a conventional crystal, by forming into a lattice of atoms, breaks spatial translation symmetry.

Documentation is different from demonstration. Text (with graph or animation interspersed to unpack unintuitive terms) wins for documentation. Video could be good for demo if presented in a no-nonsense manner.

Step 1: “Explains” relativity with Doppler effect

Step 2: proceeds to complain others confusing relativity with Doppler effect

What other fields?

The offspring of a virgin birth are not exact clones of their mother but are genetically very similar, and are always female.

What’s the source of the difference?

Think of this as a citation gold rush. You need to get on the band wagon early to become part of “the standard references” that everyone has to cite regardless of relevance. People will avoid making outlandish claims in order not to look stupid a year later in case things didn’t work out – no follow up work thus far has actually claimed to see superconductivity, just innuendos.

Not saying LK99 is or is not the wonder material, but right now it’s more of a sociological experiment.

The point is there are established conventions among the practitioners on how these are pronounced, and not getting them right says something about the youtuber who may otherwise appear as an expert.

You might be right on how the name ‘Schrieffer’ should be pronounced in its original tongue, but I’ve heard multiple former students and colleagues of Bob Schrieffer pronounce it otherwise to conclude that theirs is probably how Schrieffer himself intended his name to be pronounced.

Yeah, can’t wait to hear economists’ take, or The Economist’s…

Hi Joe Brian

Not to be snobbish or anything, but at this juncture I wouldn’t trust anyone who can’t pronounce arXiv (or Schrieffer for that matter) correctly to explain room temperature superconductivity to me. Hell I barely believe anyone with a materials/physics degree…

Someone, please, rephrase the title!

Hahaha, but to be fair, high Tc now typically refers to above the nitrogen boiling point of 77K, so 20K is a bit low even for them. I think the reference to 20K is in distinguishing between conventional vs unconventional superconductors–depending on if they can be explained by the BCS theory. When unconventional superconductor was first discovered, the highest known Tc for the conventional ones was about 20K. One could even say, therefore, calling it “high” is just experimentalists flexing to theorists.

Hey, I have am 1 atom, how many do you have are you?

I think it’s more nuanced though. It’s more like theory helps us understand the underlying mechanisms of many phenomena, but the lack of precise measurements for initial conditions, together with the existence of chaos, makes robust long-term predictions out of reach.

I mean this idea is not new – Poincare had similar opinions in the 19th century iirc. The only thing the author said differently is that the universe is like an animal, and only in the last paragraph offhandedly for that matter.

Here is a more in-depth companion article from APS. It sounds more like technical difficulties in performing a theoretical calculation than a problem with the fundamental theory

Link to arxiv