Year-end linkage

A mathematician’s unanticipated journey through the physical world (\(\mathbb{M}\)). Quanta profiles Lauren Williams and discusses her work on enumerating cells of Grassmannians and its unexpected connections with intersection patterns of solitons.

Connecticut state university system faculty contract negotiations go sour (\(\mathbb{M}\)). Proposals include increasing units taught per term, adding a term, halving units counted per hour of teaching, doubling required office hours, killing a cap on part-timers, adding required weekend teaching, eliminating faculty ownership of course content, eliminating funds for faculty travel and research, eliminating committee review of personnel actions, and monitoring emails for union activity.

Pat Morin implements the product structure for planar graphs in Python (\(\mathbb{M}\)). This is part of a recent line of research in which planar graphs can be decomposed as subgraphs of strong products of paths with bounded-treewidth graphs. Pat writes: “Not exactly industrial-strength, and leans towards simplicity over performance. Still, it can decompose 100k-vertex triangulations in a few seconds.”

Modular origami polyhedra systems (\(\mathbb{M}\)). An old link by Rona Gurkewitz from my Geometry Junkyard, moved to a new address.

Socrates as anti-democratic enabler of tyrannical coups (\(\mathbb{M}\)). None of this analysis is particularly new, but it’s not the version of Socrates you’ll see when you look at the Wikipedia article.

Blichfeldt’s theorem (\(\mathbb{M}\)): Any set in the plane of area greater than one can be translated to contain two integer points. New article on Wikipedia, connected to an expansion of the biography of Hans Blichfeldt, who came to the US from Denmark as a teenager in 1888 and worked for several years as a lumberman, railway worker, and surveyor before his mathematical talent was recognized and he became one of the first students at Stanford.

I’ve been experimenting with git-svn (\(\mathbb{M}\)), for a new project whose coauthors chose svn. It somehow manages to be clunkier than either svn or git by themselves. I understand why svn’s linear history forces compromise, but mostly I tend to keep a linear history anyway. I just want git pull and push to work, but instead I have to learn new un-mnemonic commands (for which the cheatsheet of equivalences from svn to git-svn was helpful). The only advantage over svn that I found was you have a local copy of the history, although in the comments David Bremner suggests more.

“Why I never ‘agree to disagree’ — I just tell you when you’re wrong” (\(\mathbb{M}\)). Los Angeles Times columnist Michael Hiltzik on truth versus neutrality, and why it is incorrect and intellectually lazy for public media to treat certain firmly-established facts — such as the existence of the COVID pandemic, the outcome of the recent US election, or human-driven climate change — as topics on which debate is still reasonable.

The perfect Christmas cookie cutter: one that tessellates your cookie dough sheet with Christmas trees (\(\mathbb{M}\)).

Using gradient descent to find Christmas-tree-shaped fractals (\(\mathbb{M}\)).

Lars Arge died of cancer on December 23 (\(\mathbb{M}\)). You can read an obituary by his department chair and another by Suresh Venkatasubramanian. Lars was a leading researcher in algorithms for massive data, and an anchor for algorithms and computational geometry in Denmark. As Suresh writes, he was a larger-than-life figure; we’ll miss him.

Reinhardt polygons (\(\mathbb{M}\)). These polygons have equal side lengths and are inscribed in Reuleaux polygons. Among all convex polygons with the same number of sides (any number that is not a power of two), they have the largest possible perimeter for their diameter, the largest possible width for their diameter, and the largest possible width for their perimeter. New Wikipedia article.

Moshe Vardi suggests taking advantage of this year’s disruption to the dysfunctional computer science conference publication system by setting up a replacement that is more scalable and doesn’t involve large amounts of carbon-expensive travel (\(\mathbb{M}\)). He doesn’t really say what this new system (or old journal system?) should be, though, only that we should design it.

Relatedly, IEEE relents on corrections to conference papers.

What winter looks like in different parts of the world. Long photo-thread responding to a request by Christian Lawson-Perfect’s 3-year-old. Here’s my contribution, with prickly pears and the distant snow-topped San Gabriel mountains in Southern California:

Game of Life running on Penrose tiles (\(\mathbb{M}\)). With links to a New York Times feature of “short reflections from big thinkers on why Conway’s famous cellular-automata gewgaw remains so fascinating”. From which I found Kjetil Golid’s generative-art crosshatch automata.

Two analyses of citation vs other impact in mathematics (\(\mathbb{M}\)):

• In “Don’t count on it” in the Notices, Edward Dunne compares highly cited mathematicians to winners of multiple prizes; high citations clustered in few topics, while prize winners were widely distributed across research areas.

• In “Citations versus expert opinions” (arXiv:2005.05389, via retractionwatch), Smolinsky et al compare highly cited papers to MathSciNet featured reviews, again finding little overlap.