Two recently-posted geometry puzzles (neither of which I have seriously attempted to answer):

(1) : If you expand a convex polygon along one coordinate axis while leaving the other coordinate unchanged, can the original polygon always fit into the expanded copy (perhaps with some rotation or translation)?

(2) : How many different integer rectangular cuboids have (ignoring units) volume = surface area?

O(n^2) in Windows Management Instrumentation:, via

This is why understanding algorithm analysis is important: even when the constant factors are very small (here, a nine-instruction loop), quadratic time can mean significant delays.

The post also introduces "Dawson’s first law of computing: O(n^2) is the sweet spot of badly scaling algorithms: fast enough to make it into production, but slow enough to make things fall down once it gets there."

Chalkdust magazine provides a compass-and-straightedge construction for the girih pattern on the cover of a recent issue:

Also while I'm picking on Wiley, how did the following paper ever pass peer review for their journal _Concurrency and Computation, Practice and Experience_ (or even a basic sanity check that it has a coherent topic that fits the mission of the journal?

This image by Adam Majewski from shows the osculating circles of an Archimedean spiral. The spiral itself is not shown, but you can see it anyway, where the circles become dense.

It is not unusual that the circles nest. By the Tait–Kneser theorem ( this happens whenever the curvature along a curve is monotonic. And on most smooth curves, the curvature is monotonic except at a small number of points called vertices.

My mother has a new book of poetry coming out:

I think this is her fifth, after Earthward (Finishing Line Press, 2014), Rogue Wave at Glass Beach (March Street Press, 2009), Quickening (March Street Press, 2007), and A Place Called Home (Monday Press, 1995).

The surprising link between recreational math and undecidability ( Evelyn Lamb describes how a seemingly isolated fact about Fibonacci numbers (\(F_n^2\vert F_m \Rightarrow F_n\vert m\)) led to Matiyasevich's solution to Hilbert's 10th problem, that there is no general algorithm for solving Diophantine equations.

More stupid commercial journal publisher tricks: Wiley won't honor my institutional subscription unless I enable third-party cookies in my browser. So I can (1) decrease my browser security on all sites (2) not read papers by László Babai on J. Graph Theory, (3) ask my librarian for a copy, making much more work and delay for all but maybe letting the publisher know how much negative value-added they're providing, or (4) become a pirate.

Sci-Hub ( to the rescue! Yo ho!

Davis student newspaper provides thorough roundup of sexual harassment charges against Yuval Peres:

They missed the side drama of sockpuppets and meatpuppets cleaning this from his Wikipedia article, though ( or maybe omitted it for lack of evidence connecting it to Peres himself.

This is sad. Why would someone with so much to give to the field be so self-destructive and so destructive of the lives and careers of others around him?

Mathematicians Abigail Thompson and Izabella Laba on mandatory diversity statements: and (via and

Thompson sees mandated loyalty to political positions (such as prioritizing diversity) as anti-academic freedom. Laba disagrees but prefers institutional action to lip-service statements of good intentions, and argues that unrealistic expectations on faculty benefit men with uncredited wife assistants.

American computer scientist arrested for giving a talk at a conference (on the general principles of cryptocurrency, at a conference in North Korea):

0xDE boosted

The Nefertiti Bust Meets the 21st Century:

Interesting essay on claims of intellectual property on ancient artifacts (in this case a high-resolution 3d scan of a bust of Nefertiti), clearly invalid under both US law and still-being-implemented EU law and "dangerously close to committing copy fraud". Via

Some recent open-access conference proceedings: 27th European Symp. on Algorithms (ESA),; 30th Int. Symp. on Algorithms and Computation (ISAAC),; 22nd Japan Conf. on Discrete and Computational Geometry, Graphs, and Games (JCDCGGG),

JCDCGGG is not very selective (think CCCG but more so), but I have a paper there with several co-authors on ununfoldable polyhedra with few vertices; see

New blog post: Recoloring infinite paths,

Or, how changing the colors in a 3-coloring of an infinite graph is like being stuck in Thanksgiving holiday weekend traffic.

Bechdelgrams illustrate of whether a movie passes the Bechdel test:

A nice use of color to highlight the information you're looking for in a social network: Here, the network consists of interactions between characters in a film, and the women and conversations not about men are given distinctive colors to show the test criteria: does the film have at least two named female characters, who speak to each other, about something other than men?

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A Mastodon instance for maths people. The kind of people who make \(\pi z^2 \times a\) jokes. Use \( and \) for inline LaTeX, and \[ and \] for display mode.