Linkage

Lots of flat foldable structures with arbitrary cross-sections. Images from a talk whose slide titles appear to be related to “Generalizing rigid-foldable tubular structures of T-hedral type”, a 2023 preprint by Sharifmoghaddam, Maleczek, and Nawratil.

My university went online for a day, after an anti-Israel protest encampment was shut down by and cleared by police, resulting in 50 arrests (\(\mathbb{M}\)). Negotiations between the protesters and the university administration broke down a week earlier, with some protesting students getting suspended and banned from campus, after what our chancellor and the rumor mill tell us were impossible demands from the protest negotiators calling on the campus to forbid all researchers from contact with Israelis, censor its faculty and students from expressing opinions out of line with the protesters, shut down support groups for Jewish students and Jewish studies, and close the campus police department (something that would predictably lead to less-friendly policing from less-local departments, as in fact happened when the shutdown brought in many police from nearby towns). Despite all that, the administration had been prepared to let them continue their protest indefinitely as long as it remained peaceful and did not impede other university activities. The trigger to the police action was the protesters taking over and barricading one of the main campus lecture halls.

Wikidata to split as sheer volume of information overloads infrastructure (\(\mathbb{M}\)). The proposed split is between scholarly citations (maybe 1/3 of wikidata content) and everything else. It’s not clear to me what the actual workload balance is, though. Scholia (https://scholia.toolforge.org/), a front end for the citation database, is pretty UI-intensive, but I think most of that is served up by toolforge rather than wikidata itself. On the other hand, every time you look at a Wikipedia article, it involves one or more wikidata searches, for instance to look up the links to articles in other languages, or the “authority control” data linking articles to various national databases.

Columbae House, the co-op I lived in and belonged to in college, is threatened with losing its identity and becoming just another student residence (\(\mathbb{M}\)). After student protests, the threat was lifted.

Inside Higher Education on the phenomenon of professors with established positions going on the job market to get a counteroffer to stay at their old position with improved conditions (\(\mathbb{M}\), archived). I think it is well known that this benefits men more than women because of societal pressures that make women less likely than men to try playing this game. But the linked article reports on a different way that this system increases bias: “women and faculty of color who receive outside job offers are far less likely than their white, male peers to receive a counteroffer to stay at their current institution”.

Bell numbers count the partitions of a set. But as John Baez describes, they also give the moments of a Poisson distribution: the \(n\)th Bell number is the expected value of the \(n\)th power of the number of Poisson-distributed events. This is known as Dobiński’s formula.

Online historical mathematics textbooks (\(\mathbb{M}\)), focusing on English-language algebra and arithmetic texts from the 16th to 19th centuries.

Recent salary increases for graduate-student teaching assistants at the University of California have left lecturers behind, causing situations where the Ph.D.-holding instructor of a course gets less pay than the master’s student hired to be their assistant, leading to hurt feelings and badwill (\(\mathbb{M}\), archived). Both the graduate students and the lecturers are represented by unions, but these inversions happened after the students struck for a new contract, while the current lecturer contract extends until 2026. It doesn’t look like local administrators can do much to work around the problem, and a higher-level university spokesperson issued only a bland statement saying essentially that they think they pay lecturers well already (obviously not) and that this would be on the table the next time negotiations roll around.

xkcd on a “one-bit Bloom filter” (\(\mathbb{M}\)). But isn’t this really a zero-bit filter?

Accepted papers from the Canadian Conference on Computational Geometry, CCCG 2024 (\(\mathbb{M}\)), to be held in mid-July at Brock University.

The perils of living at a house with a fractional address (\(\mathbb{M}\), archived). I recently covered the list-labeling problem in my graduate data structures course; it’s an online problem where one must assign ordered numbers to the elements of a dynamic totally ordered set, not unlike the building numbers along a street, but where (unlike building numbers) occasional renumberings are allowed. It’s amusing from afar to see what happens when you get it wrong and are forced into using fractional numbers, but it would be less amusing to live at one of those addresses that online businesses will not deliver to.

Vesa Timonen finds a four-piece miter to square dissection. The miter is a non-convex pentagon formed by slicing a square diagonally into quarters and removing one of the quarters. Sam Loyd thought he had a four-piece dissection, but he was wrong, and Dudeney conjectured that five pieces was the minimum. It turns out he was also wrong. The new dissection is very different from Loyd’s.

On announcements of mathematical results before a full proof is available. David Wood argues that after a two-year grace period with no complete version written (and preferably made public) the announcement should be considered retracted and its problem unsolved. The link and linked discussion includes multiple examples.

Celtix (\(\mathbb{M}\)). Andrew Taylor prototypes a puzzle of linking specified points by celtic-inspired knotwork.

Small-volume bodies of constant width (\(\mathbb{M}\), via). Answering a question of Oded Schramm, this new preprint by Arman, Bondarenko, Nazarov, Prymak, and Radchenko shows that the volume of a body of constant width can be exponentially small in the dimension, relative to the volume of a ball of the same width.