Linkage

There are many good articles on women in mathematics in the March 2022 Women’s History Month issue of the Notices of the AMS (\(\mathbb{M}\)).

Otter, a speechtotext transcription app frequently used by journalists, and other similar apps, may expose the identities of confidential sources to third parties including ad trackers, law enforcement, and national security forces (\(\mathbb{M}\), via). There’s no evidence that Otter is any better or any worse about this than any other cloud data system. This is simply what happens when you entrust your data privacy to other people’s computers.

A problem that seems highly suited to current machine learning techniques: learn to keep a tokomak fusion reactor’s plasma under control (\(\mathbb{M}\)). As a famous quote from Edward Teller goes, this is “like trying to hold a blob of jelly with rubber bands”. So far tested only in simulation but claimed to have good results in that testing.

Bad user interface design in Google Slides (\(\mathbb{M}\), via). I use beamer for my slides, though, and that’s not exactly designerfriendly, so I guess I have no basis for pointing fingers.

Proof of Euler’s formula for convex polytopes by induction on dimension, projection of their Schlegel diagrams, and redistribution of charges from faces into facets (\(\mathbb{M}\)), based on a paper by Petr Hliněný at EuroComb 2021, “A short proof of Euler–Poincaré formula”. Adding this also gave me the opportunity to revamp my old and crufty Euler formula proof site to use MathJax, format properly on mobile devices, and validate as html.

Another roundup of recent Wikipedia Good Articles (\(\mathbb{M}\)):

Antiparallelogram: cross two sides of a parallelogram for this useful 4bar linkage.

Threegap theorem: points \(i\theta\) for \(i=0,1,\dots, n\) partition a circle into arcs of at most three lengths; applied in plant growth and music theory.

Infinity symbol: you know, \(\infty\).

Bonus Good Article, not one I was the main contributor to: Affine symmetric group, the group of symmetries of the triangular tiling of the plane and analogous higherdimensional structures.


Ghosts in the tiling (\(\mathbb{M}\)), an article by Tim Lexen from a year ago on shapes with circulararc boundaries, pairs of shapes where the arcs of one shape are at the vertices of the other, and how tilings of these shapes correspond to the arrangements of their paired shapes.

I had this link taking up space in my bookmarks for far too long, and I ran out of better things to post, so: Hypatia of Alexandria and the Seven Presocratics (\(\mathbb{M}\)), Existential Comics. But don’t pay any attention to the potted biography after the comic; it’s based on an early20thcentury American work of moralistic historical fiction for children with little connection to any actual history of philosophy.

International Congress of Mathematicians to be fully virtual and hosted outside of Russia (\(\mathbb{M}\), via, see also), replacing the inperson meeting scheduled for St. Petersburg. This step was urged by many major national mathematics societies because, as the Australians put it, the attack made impossible the “safe and open atmosphere of collegiality and friendship” necessary for such an event.

Continued misbehavior by Elsevier at the corporate level (\(\mathbb{M}\), via), separate from their academic publishing business: this time it’s not gunrunning, it’s fossil fuel advocacy. But they’re not alone: Taylor & Francis and Wiley also have fossil fuel industry ties.

Prompted by a recent numberphile video “Sculpting with tetrahedra” (\(\mathbb{M}\)) in which Marcus du Sautoy discusses the symmetries of shapes formed by gluing regular tetrahedra and how that informed the art of Conrad Shawcross, I found this story: Youth outwits merit exam, raising 240,000 scores, New York Times, 1981. The incorrect PSAT question was: glue a regular tetrahedron onto a triangular face of a square pyramid. How many faces does the resulting shape have?

Planar graphs are 5degenerate (\(\mathbb{M}\)): you can reduce them to nothing by repeatedly removing vertices with at most 5 neighors. One seemingly overpowered proof is to represent the graph by a circle packing and sort vertices by circle size. In “Bounding generalized coloring numbers of planar graphs using coin models”, Nederlof, Pilipczuk, and Węgrzycki observe that this method has additional useful properties: in particular few larger circles can be reached by short sequences of neighboring circles where each step except the last decreases the radius.

Genderneutralizing academic titles: University of Oregon replaces “professor emeritus” and “professor emerita” by “professor emerit” (\(\mathbb{M}\), see also). Plural “emerits”. Takeaway quote from an editorial on the subject by Jennifer J. Freyd, re emerita: “It’s like calling me a professorette now”.