0xDE

I'm a computer scientist at the University of California, Irvine, interested in algorithms, data structures, discrete geometry, and graph theory.

Public Key

npub1r0rmlr8tq9rpk40ungugany0ywdnkeftk997zpvuwjjtdq4k6quqck9e4y

NIP-05 Address

11011110@mathstodon-xyz.mostr.pub

Profile Code

nprofile1qqsph3al3n4sz3sm2h7f5wywej8j8xemv54mzjlpqkw8ff9ks2mdqwqa9l35k

Author Public Key

npub1r0rmlr8tq9rpk40ungugany0ywdnkeftk997zpvuwjjtdq4k6quqck9e4y

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Last Notes

2024-12-22 23:03:13

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@nprofile…ucsf To my ears it's a form of address a movie mobster would say rather than anyone in real life

2024-12-22 21:43:18

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@nprofile…ucsf I don't know, looks kind of threatening in US English too

2024-12-20 17:35:34

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@nprofile…fa4k The two goals are a little contradictory: the new mathematics Wikipedia editors are the ones who tend most to write for themselves rather than for a general audience. But they also tend to get better over time.

2024-12-20 01:22:01

I have a new paper _Princ-wiki-a Mathematica_: Wikipedia Editing and Mathematics, https://www.ams.org/journals/notices/202501/noti3096/noti3096.html, in the January _Notices of the AMS_, and a new blog post, Pseudonymity in academic publishing, https://11011110.github.io/blog/2024/12/19/pseudonymity-academic-publishing.html
The _Notices_ paper is on editing mathematics on Wikipedia, and I hope it encourages more to do so. The blog post is on the fact that the AMS would not let us list our pseudonymous coauthor as an author. Pseudonymity is important and highly protected on Wikipedia, in part because Wikipedia editing can sometimes put its editors into serious danger, but in this case it clashed with academic publishing standards, or at least the AMS's publishing policies, and I wanted to explore that.
Some of the other material in this issue also looked interesting to me, especially @nprofile…qmju's article on machine-assisted proof (https://www.ams.org/cgi-bin/notices/nxgnotices.pl?next=202501) and Nick Trefethen's on rational approximation (https://www.ams.org/journals/notices/202501/noti3066/noti3066.html). See https://www.ams.org/cgi-bin/notices/nxgnotices.pl?next=202501 for the whole issue.

2024-12-17 18:03:05

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@nprofile…yu7x There are some other differences than symmetry between your version and this one. Yours has three half-twists rather than one, and in the limit of rollers whose radius and distance from each other gets as small as possible (for a fixed belt width) its limiting form is a hexagon, because the three belts cannot simultanously overlap in the center. In this form, instead, there is only one half-twist, and a limiting form that is a smaller equilateral triangle, making the shortest possible flat rectangular Möbius band of a given width (see Schwarz, https://arxiv.org/abs/2308.12641).

2024-12-17 04:59:33

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@nprofile…yu7x It's pretty easy to make a flat Möbius strip in 3d with three horizontal strips on three different horizontal planes, connected by cylindrical rollers.
In this schematic top-down projected view, the centerline can be any triangle, the rollers are perpendicular to the angle bisectors, and the diameter of each roller is the distance between two of the three horizontal planes. The actual geometry would be slightly different (the projected outline of the belt would curve as it passes around each roller) but not in a way that prevents the surface from being constructed like this.
https://media.mathstodon.xyz/media_attachments/files/113/666/371/063/884/444/original/05fd75223ea3a74c.png

2024-12-16 19:46:50

"Since 2012, five Wikipedia editors have been imprisoned – and one executed – for the crime of contributing to the world's largest online encyclopedia": https://boingboing.net/2024/12/16/from-keyboard-to-prison-cell-the-dangerous-side-of-wikipedia-editing.html

2024-12-13 18:46:15

New Zealand halves its funding for basic research and cuts all such funding in social science and humanities: https://www.science.org/content/article/amid-cuts-basic-research-new-zealand-scraps-all-support-social-sciences, via https://news.ycombinator.com/item?id=42405956

2024-12-03 08:04:06

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@nprofile…cas5 @nprofile…fa4k Re higher dimensional extensions of Pick: one obstacle is the Reeve tetrahedra (https://en.wikipedia.org/wiki/Reeve_tetrahedra), which have different volumes but that look the same as each other with respect to counting interior and boundary lattice points.

2024-12-03 05:29:41

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@nprofile…fa4k @nprofile…cas5 Isn't it the same for any lattice? Area = (Pick formula) * fundamental parallelogram area = (Pick formula) * 2 * (triangle area)

2024-11-24 20:24:38

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@nprofile…saev @nprofile…sp4m If they were regular the 3-hex vertices would have to be flat. I mentioned this example in https://ics.uci.edu/~eppstein/junkyard/ukraine/ukraine.html (where I called it, maybe inaccurately, a truncated rhombic dodecahedron), because it's a zonohedron.

2024-11-24 08:39:43

For-profit academic publishers love LLM garbage: Kevin Munger on Crooked Timber, https://crookedtimber.org/2024/11/08/for-profit-academic-publishers-love-llm-garbage/
Munger argues that under current open-access pay-to-publish standards, they make a profit on each LLM-produced paper, are motivated primarily by profit, and have little short-term incentive to make their journal content meaningful to subscribers. Therefore, if we want to continue to be able to find meaningful scholarly content, we need to look elsewhere than these publishers. Munger advocates diamond open-access instead, cutting out the profit motive.

2024-11-13 08:15:27

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@npub1knz…c73p A fox for every henhouse

2024-11-12 23:54:03

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@npub1c9m…9xjd @npub1ez3…xnxl I've gotten in the habit of following those links by opening a new browser tab. That way I come back, if only to close the tab.

2024-11-12 02:33:39

Lower bounds for adaptive relaxation-based algorithms for single-source shortest paths: https://arxiv.org/abs/2411.06546, by Sunny Atalig, Alexander Hickerson, Arrdya Srivastav, Tingting Zheng, and Marek Chrobak, to appear at ISAAC 2024.
This is part of a line of work including a paper of mine at WADS 2023 (see https://11011110.github.io/blog/2023/05/17/permutation-supersequences-shortest.html and https://arxiv.org/abs/2305.09230) where I proved that, among shortest-path algorithms that perform relaxation steps in a fixed order, depending on the graph but not on the results of previous steps, Bellman-Ford is within a constant factor of the optimal number of steps. In https://arxiv.org/abs/2402.10343, Jialu Hu and László Kozma eliminated the constant factor for deterministic algorithms on complete graphs, as a result showing that an older paper of mine, on a randomized version of Bellman–Ford (https://11011110.github.io/blog/2011/04/11/randomized-bellmanford.html and https://arxiv.org/abs/1111.5414) is strictly better than deterministic for this case. The new paper extends these results in a different direction, to algorithms whose order of operations depends (in a restricted way) on the results of previous operations, as you would want to do in any practical implementation of Bellman–Ford. For instance, once an edge has been relaxed, there's no point in doing it again until some other step has caused the distance to its starting vertex to improve.
If you want to see this at ISAAC, in Sydney, Australia, December 8–11, you need to preregister! Registration is open only until November 29, and will not be available at the conference. See https://sites.google.com/view/isaac2024/registration (via https://kamathematics.wordpress.com/2024/11/11/guest-post-isaac24-in-sydney-registration-deadline-soon/). And for the full list of ISAAC papers, see https://sites.google.com/view/isaac2024/list-of-accepted-papers

2024-11-09 17:40:43

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@npub1yxx…p7am Almost the same as the one I drew at a time, https://11011110.github.io/blog/assets/2024/gappy-packing.svg
The difference is that you have the very narrow gap between the top square and the central triangle below it; I shifted the triangle so that gap is on the other two edges of the central triangle. All angles in my drawing are multiples of 15°.

2024-10-30 21:35:51

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@npub1c9m…9xjd Now about that overly-dark roast...

2024-10-26 07:29:12

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@npub1knz…c73p Cute. But there appears to be a missing constraint in the description of how to do this: the green triangles need to be separated from each other in order to make the yellow net be a simple polygon. That is not true for all 11-gons. Also, your drawing shows a convex 11-gon, but that is not necessary; the same procedure can work for non-convex 11-gons (I don't know whether the proof that all polyhedra of this type can be represented in this way requires non-convexity).
https://media.mathstodon.xyz/media_attachments/files/113/372/541/416/673/757/original/de28ee9aac1cd9db.png

2024-10-20 07:32:44

Pentagonal bipyramids lead to the smallest flexible embedded polyhedron: https://arxiv.org/abs/2410.13811, new preprint by
Matteo Gallet, Georg Grasegger, Jan Legerský, and Josef Schicho
Convex polyhedra are rigid, but some special non-convex polyhedra have at least one continuous degree of freedom. (More than one degree of freedom can be obtained in a trivial way by gluing such polyhedra.) The Bricard octahedra (https://en.wikipedia.org/wiki/Bricard_octahedron) have the same combinatorial structure as a regular octahedron, and can sort of flex, but only if you allow faces that can cross through each other. You can avoid the crossings, for instance by making little gussets near where they would happen, at the expense of making the shape more complicated.
It was believed that Steffen's polyhedron, with 9 vertices, 21 edges, and 14 triangular faces, was the simplest possible non-self-intersecting flexible polyhedron. For instance, Demaine and O'Rourke's book _Geometric Folding Algorithms_ (p. 347) writes "As it was later proven that all triangulated polyhedra of eight vertices are rigid, Steffen’s example is minimal in this sense."
But it was apparently not proven, and the new preprint claims a better example: an 8-vertex polyhedron formed from a pentagonal bipyramid by subdividing one triangle into three. This seems a bizarre choice because this subdivision does not affect flexibility. But it can act as a gusset pulling two parts of the boundary away from each other, changing a self-crossing bipyramid into a non-self-crossing subdivided bipyramid.

2024-10-18 04:22:27

New blog post: Splines for graph drawing theory, https://11011110.github.io/blog/2024/10/17/spline-graph-drawing.html
Related new arXiv preprint: Drawing Planar Graphs and 1-Planar Graphs Using Cubic Bézier Curves with Bounded Curvature (with Mike Goodrich and Abraham Illickan), https://arxiv.org/abs/2410.12083

2024-10-17 01:30:08

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@npub1knz…c73p Typo: Nima, not Nina

2024-10-15 23:26:50

I'm sure many have seen https://stallman-report.org/ detailing Richard Stallman's misconduct and how it and his enablers have harmed the free software movement. Much of this is not new but I was still shocked by a line early in the "Why publish this report?" section: "Women represent just 3% of the free software community, compared to 23% of industry programmers generally." Obviously not all of that disparity can be attributed to #Stallman alone, but his continued position of prominence is a symptom of a broader disease in the community's culture. Paying attention to these problems rather than turning a blind eye to them is a necessary step towards healing.

2024-10-15 17:34:38

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@npub1yxx…p7am Can't hurt to try.

2024-10-07 00:52:15

New blog post: a half-flipped binary tiling, https://11011110.github.io/blog/2024/10/06/half-flipped-binary.html
Mostly an excuse to show and explain the following image:
https://media.mathstodon.xyz/media_attachments/files/113/263/386/426/684/610/original/e1524ee94a3f12ef.png

2024-10-01 01:28:49

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@npub1knz…c73p @npub1yt3…wmv6 This all seems unnecessarily indirect. If they want to reduce their quality standards so that they let more badly-written AI-generated slop through in place of actual research papers, in order to generate training data, why not just cut out the middlemen and use an AI to generate badly-written slop to use as training data?
Or maybe they think that they can escape the inevitable lawsuit for violating the terms of their data-supply contract by pointing to the authors and saying they are shocked, shocked to discover that the kind of author who would go for a cut-to-nothing review process would also use AI to help write their submissions?

2024-08-16 06:23:18

Congratulations to Rajeev Alur of the the University of Pennsylvania for winning the 2024 Knuth Prize (https://www.sigact.org/prizes/knuth/citation2024.html) "for his introduction of novel models of computation which provide the theoretical foundations for analysis, design, synthesis, and verification of computer systems"!

2024-07-11 20:34:55

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@npub17nm…dm57 I found an all-four-wall-touching solution to Celtix #24 with 18 walls. I have no idea whether that is optimal.

2024-07-09 17:48:47

Journal publisher caught adding falsified citations (citations that do not appear in their actual published papers) through the metadata they supply to bibliographic databases: https://theconversation.com/when-scientific-citations-go-rogue-uncovering-sneaked-references-233858, https://arxiv.org/abs/2310.02192

2024-07-08 22:23:29

Scott Aaronson on "the Zombie Misconception of Theoretical Computer Science" (https://scottaaronson.blog/?p=8106): the mistaken idea that concepts like NP-completeness and uncomputability (which apply to functions or infinite sequences) can instead be applied to individual values and individual yes-or-no questions.

2024-07-06 18:56:18

Bookends #caturday
https://media.mathstodon.xyz/media_attachments/files/112/741/051/911/974/758/original/d2fe1f98f8896f4d.jpg

2024-06-26 18:13:34

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@npub1c9m…9xjd The problem is that there are probably more likely voting procedures than members of your club. But almost anything works when the participants are all trying to cooperate.

2024-05-26 05:01:27

xkcd on "one-bit Bloom filter" (but isn't this really a zero-bit filter?): https://xkcd.com/2934/
Also, @xkcd seems to have stopped updating a couple weeks ago; anyone know what happened or how to get it going again?

2024-05-13 06:17:34

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@npub1fpe…75rh Yes, I saw a later story from El País (in Spanish) noting an unprecedented number of blank ballots from the faculty, the only way to dissent.

2024-04-28 19:40:02

El País on the questionable self-citation habits of AI/cybersecurity researcher Juan Manuel Corchado, the sole candidate for rector at the University of Salamanca: https://english.elpais.com/science-tech/2024-04-26/the-seven-lies-of-the-ai-expert-who-cited-himself-thousands-of-times-on-scientific-papers.html (via https://news.ycombinator.com/item?id=40190136; see also http://retractionwatch.com/2022/03/25/how-critics-say-a-computer-scientist-in-spain-artificially-boosted-his-google-scholar-metrics/ from 2022)

2024-04-21 23:21:04

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@npub17nm…dm57 But what do you think of pool noodles?