pglpm

The question of what an electron really is, is still open as far as I know. Even the question of whether it's a "particle", is still open. In many or most theories the question of "what it is" is somewhat bypassed. In quantum field theory you describe electrons as a field (like the electromagnetic field), but all fields have the peculiar property that they show energy exchanges in very localized, point-like regions of space – that's why you can think of them as particles sometimes. Take a look at Wald's book to get an idea.

There are even still open theories that try to describe electrons as mini charged black holes; not to speak about strings, and so on...

The usual misleading sensationalistic title. It isn't the "shape of the electron" at all. A less misleading – but still not quite correct – explanation is that they have determined the statistical distribution of electron quantum states in a material. Very roughly speaking, it tells us where we're more or less likely to find an electron in the material, and in what kind of state. Somewhat very distantly like a population density graph on a geographical map. Determining such a population density doesn't mean "revealing the shape of a person".

The paper can also be found on arXiv. What they determine is the so-called quantum geometric tensor. I find the paper's abstract also misleading:

The Quantum Geometric Tensor (QGT) is a central physical object...

but it's a statistical object more than a "physical" one.

It's a very neat and important study, and I don't understand the need to be so misleading about it :(

Cheers! for some reason my search didn't bring that up!

Unfortunately they cannot yet be resized on the fly, as instead some vertical-tab extensions allow you to do. But it's a step in the right direction!

Cheers! 🙏 Unfortunately it's the same as on Sci-Hub, the "accepted version". It'll have to do.

Restored! Maybe worth a post update?

https://open-slum.org/

Figuratively or for real?

I'm actually a physics teacher 😂 In fact, as I write in the post, these questions are more about self-reflection. They bring to light some interesting points or issues about Newtonian mechanics and the way we teach it.

Please see my replies in the cross-post https://lemmy.ca/post/33867210

Completely agree, which I think is very interesting. In Newtonian mechanics, some scalar and vector quantities such as mass, internal energy, contact forces (stress), heat flux are frame-indifferent. Others, such as velocity and acceleration, are frame-dependent but we do have transformation rules for them. Some quantities – and quite important ones – such as momentum, are in a sort of limbo: they are frame-dependent, but there's no clear transformation rule for them.

From the point of view of relativity theory, it's interesting to note that for this particular case of coordinate transformation – note that it is not a Lorentz boost – we can actually calculate the spatial components of momentum in the new coordinate system, if the reported momentum is expressed as a covariant vector (p_µ). This is because its unknown temporal component (energy) gets multiplied by zero in this transformation. But the text is ambiguous on whether the reported components are covariant or contravariant.

Regarding the third body, consider the case where its mass is, say, 2 kg, and the case where it's 1 kg instead (the momentum being the same).

Yes we're considering Newtonian mechanics in any case. What I'm especially curious about is what physical principles people use to motivate their answers.