Linkage

Ars Mathemalchemica: From Math to Art and Back Again (\(\mathbb{M}\)), article in the Notices by Susan Goldstine, Elizabeth Paley, and Henry Segerman about the Mathemalchemy traveling multimedia mathematical art installation.

30 Years of Modularity (\(\mathbb{M}\)), well-produced and accessible number theory talk by Frank Calegary for the ICM.

At ICGT, the “detour problem” in graph algorithms was repeatedly mentioned (\(\mathbb{M}\)): Given vertices \(s\) and \(t\) in an unweighted digraph, how hard is it to find an \(s\)–\(t\) path that is not a shortest path? It’s polynomial for planar digraphs [Fomin et al STACS 2022] and undirected graphs [Bezáková et al ICALP 2017], and \(\mathsf{NP}\)-hard in the weighted case. But the unweighted problem for arbitrary digraphs remains (annoyingly) open.

Successful completion of the Liquid Tensor Experiment (\(\mathbb{M}\)), a challenge posed to the Lean prover community by Peter Scholze, after a year and a half of effort, where here “completion” appears to mean that the initial goal has been attained, but the associated repo still seems to be under active development. And apparently they are in dependency hell with mathlib.

As professionals flee antiabortion policies, red states face a brain drain (\(\mathbb{M}\), archived copy), Michael Hiltzik, business columnist for the Los Angeles Times. Despite the headline, it’s not just the antiabortion policies of the red states that are making it hard for their universities to attract good faculty and students; the column also mentions pro-gun, anti-public-health, and anti-LBGTQ policies, and restrictions on the teaching of history.

Voronoi structure headgear in fashion in South Korea (\(\mathbb{M}\)). (Sadly, not actually true.)

Linking to mathstodon.xyz from Wikipedia has been blacklisted, I think for the last two years, as part of a general prohibition on .xyz links as mostly spammy (\(\mathbb{M}\)). I successfully petitioned for it to be whitelisted, and linking has become possible again. I don’t recommend this for Wikipedia articles themselves (mathstodon isn’t likely to meet Wikipedia’s standards for reliable sourcing) but it could be relevant on some discussion pages.

University and film colleagues mourn death of leading film and television academic Geoff Lealand (\(\mathbb{M}\)). Geoff was my uncle. Because of the distance from New Zealand to California I didn’t see him often, but I posted briefly from a visit by him in 2013.

Twin-width (\(\mathbb{M}\)), new Wikipedia article. This is currently a very hot topic in structural graph theory and parameterized graph algorithms, with at least 25 papers all since 2020. So probably this article will need some updating as more results emerge.

Color Blind Accessibility Manifesto (\(\mathbb{M}\), alt link), Federico Monaco, CACM.

Academic freedom threatened in India (\(\mathbb{M}\), THE, IHE). According to the story, university administrators with government ties have been “reprimanding academics for openly speaking out” against the government or against local misadministration, and keeping records of participation in protests, claiming that faculty are subject to more-restrictive rules aimed at other kinds of civil servants.

Quadrisecant (\(\mathbb{M}\)), new Wikipedia Good Article on the lines that touch space curves in four points. Why four? Because it is the maximum for generic curves. (In contrast, in 2D generic curves can cross the \(x\)-axis infinitely often.) If you view a curve from far away, most points of view see only simple crossings of two strands, but certain special viewpoints see triple crossings and even-more-special viewpoints see quadruple crossings. Those are the viewpoints on quadrisecants.

Juris Hartmanis, a Turing Award winner and leading figure in computational complexity theory for many years, died on July 29 (\(\mathbb{M}\)). These three blog posts have more about him and his contributions: Bill Gasarch; Dick Lipton and Ken Regan; Scott Aaronson and Ryan Williams.

Video on Cannon–Thurston maps (\(\mathbb{M}\), see also), space-filling curves formed from surfaces in hyperbolic 3-manifolds by lifting the boundary of the surface to the boundary of the universal cover of the manifold.