Linkage with incoming gloom

New book-sorting algorithm almost reaches perfection (\(\mathbb{M}\)): Quanta on the list labeling problem, based on “Nearly Optimal List Labeling” by Bender, Conway, Farach-Colton, Komlós, Koucký, Kuszmaul, and Saks, from FOCS 2024.

Incoming gloom (\(\mathbb{M}\)):

Origami Möbius double basket. Heading towards, but not quite reaching, the Sudanese Möbius strip, with a basketweave texture.

Using a pi divider (\(\mathbb{M}\)). I recently learned about the existence of this glassmaking tool, a simple caliper that divides a length by \(\pi\) to determine another length. If you set up a flat sheet (say of glass canes), measure it with a pi divider, and make a disk with the divided diameter, the sheet will roll up exactly around the disk to form a cylinder. (I imagine there’s an adjustment for the thickness of the sheet that in practice you would quickly learn to make when using this tool.)

Ravi Boppana has a YouTube channel of nice math explainer videos (\(\mathbb{M}\)). His newest video is on a topic of interest to me, the Erdős–Anning theorem that points in the Euclidean plane with integer distances must be collinear or finite. He doesn’t mention recent developments (such as the sublinear bound on the size of a non-collinear set in terms of its diameter or my own results on non-Euclidean distances) but instead carefully explains what is now the standard proof, by Erdős using intersections of hyperbolas. I was also interested in the oldest video on the channel, on Ron Graham’s “77 theorem”: all numbers greater than 77 are sums of denominators of Egyptian fraction representations of one. (For the finite set of numbers including 77 that are not, see OEIS A051882.)

bit.ly adds advertising interstitials to its url shortcuts. Or, why you should eschew url shorteners and un-shorten any old ones you might still be using.

The master origami artist whose collection turned to ash in Altadena (\(\mathbb{M}\), archived). Sad news about the collection of famous origamist (and coauthor) Robert Lang, from the New Yorker.

The lists of accepted papers are now public from the 2025 Symposium on Theory of Computing, STOC, to be held late June in Prague, and from the 2025 Symposium on Computational Geometry, SoCG, to be held late June in Kanazawa (\(\mathbb{M}\)). My integer distance paper got into SoCG, so that’s where I’m heading.

Journey of black mathematicians (\(\mathbb{M}\)), PBS documentary series.

On the geometric thickness of 2-degenerate graphs (\(\mathbb{M}\)), Rahul Jain, Marco Ricci, Jonathan Rollin, and André Schulz. If a graph can be reduced to nothing by repeatedly removing vertices with \(\le2\) neighbors, then it can be drawn in the plane with straight-line edges, and four edge colors, so that the edges of each color form a non-crossing forest. This answers some questions from one of my old papers, “Separating thickness from geometric thickness”.

Flintstones typewriter. A parable of the golden age, silver age, and bronze age of Google search.

For the past view days Google Scholar seems to be trying to make itself too annoying to use for me (\(\mathbb{M}\)). Some large random fraction of my searches cause it to demand that I prove I’m not a robot by identifying long sequences of captchas of motorcycles and traffic lights and palm trees. Could it be caused by the fact that its search results have become so haphazard that I keep having to re-try similar permutations of the same search phrases to find what I’m looking for? Is it trying to punish me for giving up on Chrome and only using Firefox, or for running with an adblocker? I have no idea but it makes it a much higher priority for me to find something else that works for the same task. Internet Archive Scholar still has far too spotty coverage and MathSciNet and zbMATH only work for serious mathematics, not really for computer science and not for searching for the references for basic textbook material that I often need when editing Wikipedia.

Los Angeles Times states the obvious (\(\mathbb{M}\)): Trump’s assault on science will make Americans dumber and sicker.

Video explainer of the winding problem for spiral galaxies (\(\mathbb{M}\)). If you think of a galaxy as being like the solar system’s planets with its stars in concentric nearly-circular orbits, then its arrangement into spiral arms wouldn’t be stable: the spirals would wind up tighter as the more central stars orbit more quickly than the ones in the outer arms. So the structure has to be something else – the leading theory is that it’s a density wave moving at a different speed from the stars, something like the way slowdowns can propagate through thick traffic (or even stand still) at a different speed than the speed of the traffic itself. But how this structure arises and stays stable apparently remains a bit of a mystery. If you prefer text to video, another explainer also discusses the same issue.

Unbidden, ABET preemptively falls in line with the Trump agenda to kill anti-racism and anti-sexism efforts (\(\mathbb{M}\)). This is significant because ABET controls the content of most undergraduate engineering degree programs in the US, and has historically already been hostile to non-technical general education and liberal arts requirements that might include such components.