Linkage with two breakthroughs

An exponential improvement for diagonal Ramsey (\(\mathbb{M}\)). The number of vertices needed to force either a \(k\)-vertex clique or independent set is now down to \((4-\varepsilon)^k\) for a small \(\varepsilon\). New preprint by Sahasrabudhe, Morris, Griffiths and Campos.

Josh Millard asks: where did polite numbers get their name? (See also MF.) The answer may be in a 1988 issue of The Open University’s Sesame magazine, but it appears to be offline-only.

Dehn invariant (\(\mathbb{M}\)). a value in an infinite-dimensional tensor space, determined from a polyhedron, that controls which other polyhedra it can be cut apart and reassembled into. Space-filling polyhedra must have Dehn invariant zero. For flexible polyhedra, the Dehn invariant stays constant as they flex. Now another Wikipedia Good Article.

Barriers and pathways to complexity lower bounds: relativization and algebrization, natural proofs, and new stuff (\(\mathbb{M}\)). Three one-hour lectures from a virtual seminar by Ryan Williams.

Cory Doctorow’s new hobby is finding high-priced stock image copies of public-domain art, seeking out the originals, cleaning up the scans, and making them freely available at Wikimedia Commons (\(\mathbb{M}\)).

An aperiodic monotile (\(\mathbb{M}\)). The long-sought solution to the einstein problem by Smith, Myers, Kaplan, and Goodman-Strauss. There is a lot more that could be linked here; see Gödel’s Lost Letter for a pretty good roundup.

Sad news for combinatorics: Vera Sós has died (\(\mathbb{M}\)). In Hungarian, but mostly readable through automatic translation.

The lost origin of the Lady on the Lake puzzle, in which someone on a boat at the center of a circular lake must escape someone on land who can move four times as fast as the boat. Maybe from Cambridge? Maybe from Malaysia? Maybe from papers by Guy or O’Beirne?

New Wikipedia article on a widely circulating recreational mathematics puzzle: how to divide 17 camels among three sons who are to get 1/2, 1/3, and 1/9 of the estate respectively (\(\mathbb{M}\)). It was repeatedly published in the late 19th and early 20th century, often given a vaguely oriental origin. Stockmeyer in 2013 gives the earliest of these as 1873 London. But Ageron, also 2013, while agreeing that it is not from medieval Islamic mathematics, found it earlier, in the 18th-century work of an Iranian mullah. What could be the missing link? I think I have found one: James Phillips Fletcher recounts the story in his 1850 Notes from Nineveh: And Travels in Mesopotamia, Assyria and Syria, and it was immediately taken up by newspaper puzzle columnists.

After spending too much time recently fighting unsuccessfully with editorialmanager to set up yet another account on yet another subdomain of editorialmanager.com for the sole purpose of sending one referee report to an editor, and eventually giving up and looking up the editor’s email address instead, I am strongly tempted to boycott all refereeing requests that require me to set up even more editorialmanager accounts (\(\mathbb{M}\)). It should not take this much effort to do what is essentially volunteer work for a for-profit company. They have enough money that they can pay for some usability engineers.

The hills around here are currently carpeted with California coast sunflowers (\(\mathbb{M}\)). A couple more shots.

New organ donation rules favor coastal states at the expense of the south and midwest, and lead to more unused organs (\(\mathbb{M}\)). The goal of the rule change was to fix problems where equally sick patients were prioritized unequally depending on where they live, but it has led to other problems in the place of that one.

SIGACT wants these books reviewed (\(\mathbb{M}\)). Former SIGACT News book review editor Bill Gasarch and current editor Nick Tran post a list of 16 books they need reviews for. Beyond the fame and glory of publishing a book review, if you’re in the US you can get a physical copy of the book mailed to you. (Maybe also for elsewhere but that depends on the publisher.)

Fast-growing open-access journals stripped of coveted impact factors (\(\mathbb{M}\), via). Web of Science is de-listing some 50 journals, including at least 19 from Hindawi and at least 2 from MDPI, likely in part because of these journals’ many dubiously-curated and dubiously-on-topic special issues. A consultant quoted in the article says “My expectation is that this initial delisting … is only the tip of the iceberg”.

Numbers that don’t add up: Tibetan half digits (\(\mathbb{M}\)). They’re encoded in the Unicode standards, but with one example (from a postage stamp), do we know what they’re supposed to mean?