“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!

Thanks for the pointer, I actually have accessibility turned on via bitwarden (a password manager) and never thought that might be correlated. Will test when I get the chance.

I’ve seen similar things with a physical keyboard connected. There are plenty other Android apps that can handle connected keyboards corrected by not showing the on screen keyboard(OSK) (the now defunct RIF being one). Right now the only way to not have flashing OSK is to turn it off system wide under android settings, which is not ideal (because it won’t turn itself on automatically when the physical keyboard disconnects)

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.

Education is what remains after one has forgotten what one has learned in school.

– that guy

You need to forget about the details in order to grasp the essence.

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?

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.

Scale of velocity as well so we have a more complete picture in phase space

The referees who let this slip are either brilliant or lazy (or both, I guess)

Hiw stable is this kind of density? Is it going to shrink over time?

Well, even the picture is in the picture…

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

You guys do know the affordability of the chips you’re using to comment on this is a direct consequence of TSMC “efficiency”, right?

Copy text doesn’t cut it because sometimes I just need to select a sentence or a link, not the full text.

This is also a problem for the post itself, not just comments.

On android, long press for text selection is standard operation.

Mind you, the DFT calculation from the Griffin paper is not a proof of LK 99 being a superconductor in any way. What it showed is the (potential) formation of flat bands near the Fermi surface. Band dispersion is associated with the kinetic energy of the electrons, so materials with flat band (and therefore electrons with suppressed kinetic energy) at the Fermi surface are more susceptible to interaction effect (and strong interaction causes all sorts of nonintuitive quantum effects). I’m not a DFT expert in any sense, but from what I’ve heard, it is quite easy to “tune” your model to produce narrow (the limit of which being flat) bands from substitutions (e.g. the Cu substitution in this case) and such, which don’t necessarily lead to superconductivity.

So I’ll take the DFT papers (there are quite a few now) as saying, “hey you want some flat band? Here’s some. We’ve done our part. Now some other theorist, do your magic and conjure up some superconductivity”. It’s a cog in the full picture, if there is a full picture

Step 1: “Explains” relativity with Doppler effect

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