“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))

Well the band wagon has turned 180, now it’s fashionable to point out the flaws. My issue with this kind of videos is really, where are you in the early days of the hype, when the public needed cautions the most? A convenient naysayer when all the actual hard works have been done elsewhere

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.

OK, but where are they when the LK99 first came onto scene?

Now let’s see which youtube “science channels” do a debunk on their own content pushed out a mere month ago.

Step 1: “Explains” relativity with Doppler effect

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

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.

It is waiting for reproducibility is what it is. It won’t matter much if it got published today in some no name journal – a journal is going to gamble just as this youtuber did, for the slim chance of this being true (not saying it isn’t)

Also, a quantum well is just particle in a box. Nothing fancy about it. Guy mentioned tunneling a lot but tunneling happens in metal, semiconductor, and insulator. Doesn’t really mean anything. In fact if you need to tunnel, that means there’s a chance to back scatter, so it won’t be superconducting.

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

In general you’ll be happier if less fxxk is given to someone else’s opinion. I’m not sure how important “someone else” being a parent is, other then maybe the correlation with the time spent with them or the survival resources they had control over, etc.

In fact this goes all the way back to Hamilton when he invented quaternion, in which i,j,k are used as basis vectors (which are generalizations of the imaginary i). Later Gibbs dropped the scalar component and gave us the modern vector.

For those behind a pay wall, here’s the arxiv version, https://arxiv.org/abs/2212.11841

As someone who knows nothing about high energy physics, my naive questions are: 1) why is it such a big deal that electrons don’t have electric dipole moment, but it’s OK to have no magnetic monopole, and start right at the order of dipole? 2) wouldn’t alternating domains of matter / antimatter resolve the apparent asymmetry? Has this scenario been ruled out experimentally?