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GA Review

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Reviewer: Ovinus (talk · contribs) 19:03, 11 September 2022 (UTC)[reply]

Seeing as the EMST review is finishing up, I'll grab another one. Excepting the more abstract graph theoretic concepts, I feel like this topic can be made pretty accessible to the layperson, so I'll try make suggestions toward that. Ovinus (talk) 19:03, 11 September 2022 (UTC)[reply]

That's all for now. Will do a second pass per usual after we discuss. As an aside, I realize that the letter of WP:PAREN deprecates the usage of {{harvnb}}, which is ridiculous. Haven't seen anyone instating an inferior alternative, but maybe that guideline should be adjusted to reflect actual practice. I kind of understand deprecating references like The sun is hot (Smith 1920, Doe 1999), but harvnb in this context seems totally anodyne. Ovinus (talk) 19:03, 11 September 2022 (UTC)[reply]

WP:PAREN is, literally, about references that use parentheses, and more specifically about such references in the article text. The uses of {{harvtxt}} (not {{harvnb}}, which does not use parentheses) in this article are not intended as references. You can tell that because the same text that incorporates harvtxt usages in the actual text, also has footnotes as references, which are not even always exactly the same as the names and dates incorporated into the text using harvtxt. If I were making parenthetical references in the old deprecated style, as references rather than the text of the article, they would use {{harv}}, not {{harvtxt}}. For instance, "Coxeter (1955) named..." is a piece of text, but "The Laves graph is embedded in this skew polyhedron (Coxeter 1955)." would be the deprecated format of parenthetical referencing. —David Eppstein (talk) 20:31, 11 September 2022 (UTC)[reply]
I agree with your interpretation; I just think the guideline should be edited to make that clear. Ovinus (talk) 20:51, 11 September 2022 (UTC)[reply]

Second pass

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Seeing the recent WP:ANI case I feel obligated to do some (somewhat pro forma) spot checks.

[1]: All good. [3,5]: Fine [9]: All good. For the first ref I like how it talks about duality but that's too much for this article. [10]: Can't access [15]: Fine, also WP:EXPERTSPS [21]: Fine

  • I do appreciate the spot-checking, actually. Not because it indicates a lack of trust, but because I think it should be done more generally as part of all GA reviews, and because it has a chance of turning up places where I was sloppy in sourcing or didn't myself adequately check sourcing that others put in. —David Eppstein (talk) 07:33, 14 September 2022 (UTC)[reply]
Cool, will do that going forward. I definitely don't want to be a rubber stamp, although I don't think I've been thus far in my reviews. Ovinus (talk) 08:04, 14 September 2022 (UTC)[reply]
  • For the fundamental domain (this is new math for me), my understanding/visualization is a "half-open" parallelepiped to represent the quotient , topologically a 3-torus, where is our lattice, and the parallelepiped has volume . Is that correct? I think the fundamental domain should be also announced as a "parallelepiped", for a slightly broader understanding—people probably wouldn't confuse it with some other random choice of parallelepiped. Also, this is why it'd be nice to supply the basis vectors, so that the reader can more quickly follow along with the calculation. Is there a verifiability/OR concern there?
Two different bases and two different fundamental domains for a 2d lattice
Points in a body centered cubic lattice
  • This is all pretty standard, and much of it probably sourceable in sources that talk about the body centered cubic lattice (which is what we have here, scaled by a factor of four), but I think the details are off-topic for this article. Fundamental domains are not always parallelepipeds. They can be any shape that tiles space under lattice translations. Escher's animals, maybe. For something I did recently involving 2d lattices I found it more convenient to use axis-parallel non-convex hexagons (see last image in https://11011110.github.io/blog/2022/04/03/dissection-into-rectangles.html). For the Laves graph a more intrinsic choice might be the union of four of those 17-sided plesiohedron things. For the BCC lattice, ignoring the Laves graph that it is the translational symmetries of, a simpler choice is the bottom half of the unit cube, with a tiling that arranges the half-cubes into planar checkerboards and then stacks up the checkerboards into 3d, but offset by a half-unit in each direction from one layer to the next. (These are not the parallelepipeds you would get from a basis, and their tiling is not face-to-face the way the parallelepiped tiling would be.) But you don't even need to decide on a fundamental domain in order to compute the volume. Just pile together your basis vectors as the rows of a matrix and calculate its determinant. The point of the L^3/V formula is that it is unitless, so the coordinates of your starting arrangement don't affect the result. But if we use the integer coordinates, we get four vertices and 12 halves of length- edges per fundamental domain, so total length , and a fundamental domain with the volume of a half-cube scaled by four units, so volume 32. . Also, before you ask, we should not link to Body-centered cubic lattice in this article, because that goes to an article that describes it in terms of crystallography rather than mathematics, and crystallographically the Laves graph is very different than the BCC lattice even though mathematically the translational symmetries of the Laves graph are a BCC lattice. (Part of the issue is those other symmetries that are not translations.) So the link would be much more likely to confuse than illuminate. —David Eppstein (talk) 04:55, 14 September 2022 (UTC)[reply]
Exciting! As a student I think the article fundamental domain could include a simple example in R^n that's not just a parallelepiped. It makes sense that the choice is arbitrary. Is it too off topic for even a footnote? The determinant calculation seems straightforward, and perhaps enlightening in lieu of a detailed diagram of the integer coordinates/simple basis (but perhaps not straightforward enough for WP:CALC to apply). If that particular calculation is unsourceable then meh. Ovinus (talk) 05:42, 14 September 2022 (UTC)[reply]
I rewrote this paragraph to try to make it more self-contained. —David Eppstein (talk) 07:15, 14 September 2022 (UTC)[reply]

Beyond that, I'm quite happy with the article. Discussion regarding improvements/location of my STL can go on the article talk. Ovinus (talk) 02:37, 14 September 2022 (UTC)[reply]

Oh also, how is Laves pronounced? [1] suggests /'lavəs/, but I don't know German. Ovinus (talk) 05:42, 14 September 2022 (UTC)[reply]
I don't either. That looks like it could be a German pronunciation except that I'm pretty sure the vowel marked as a schwa would have a distinct sound from other schwa-vowels that most native speakers of English would be unable to distinguish. LAH-vess not LAH-vass or LAH-vuss even though those would all sound almost the same to English and American ears and be pronounced so briefly as to be heard as a schwa. But that's only a guess. —David Eppstein (talk) 06:17, 14 September 2022 (UTC)[reply]
Unfortunate. Anyway, I quite enjoyed your new explanation, in particular the part that the edges should cross, not partially lie within, the fundamental domain—cleared my remaining confusion. Will probably pass tomorrow. Ovinus (talk) 08:04, 14 September 2022 (UTC)[reply]