Linkage

Three space-filling polyhedra in the diamond lattice (via). Along with the cube tiling usually used to show the diamond’s repeating structure, there is a rhombic dodecahedron tiling some of whose edges align with the diamond, and a Voronoi tiling with triakis truncated tetrahedra (say that three times fast!) as its cells. With pretty visualizations by Tim Hutton.

Practical applications of the subset sum problem in forensic accounting? Ryan Cavanaugh looks for Trump payments whose total matches the alleged Stormy Daniels hush money (G+).

IKEA-like algorithm visualizations from Sándor Fekete and friends.

Facebook’s canary dies (G+, via). A year ago we were warned to watch Alex Stamos’s behavior as way to track Facebook’s “weird willingess to cosy up to ultra-nationalist demagogues and authoritarian regimes”. Now he’s leaving over Facebook’s refusal to address Russian interference.

Tree drawings revisited (G+). Timothy Chan shaves logs in the area requirements for drawing trees into more exotic but also more slowly-growing functions.

Malfatti circles. Another Wikipedia Good Article, on an amusing but not-very-important problem: how to draw three circles tangent to each other and to the sides of a triangle enclosing them, and Malfatti’s mistaken belief that these would maximize the total area among all triples of circles within a given triangle (they never do). The many 19th-century researchers on constructing these circles included Charlotte Wedell, a Danish baroness who was one of four women to attend the first ICM.

Günter Ziegler on book proofs.

In praise of negative reviews. Rafia Zakaria laments the lack of critical engagement in modern book reviews, replaced by “advertisement-style frippery” and plot summary. The same criticism could be leveled at some referee reports.

Combinatorics involved with permutohedra and associahedra (G+, via). A talk by Michael Nielsen at the MAA Southeastern Conference. See G+ for how the connection he describes involving certain trees shows that the preimage on the permutohedron of a vertex of the associahedron forms a distributive lattice.

A new commission to address harassment at theory conferences (G+). I’m sure commission head Sandy Irani will handle it well, but I worry about the unnecessary emphasis on false accusations in their charge, what it says about who the audience is, and what it might do to discourage victims from reporting incidents.

Random space filling tiling of the plane (G+). Pretty images, but Paul Bourke’s somewhat-fragile generation method leads to questions of whether there’s a more robust method for this based on a nice probability space on packings.

How one prolific Wikipedian is giving voice to pre-20th century women’s stories. A profile of Wikipedian and womens’ biographer Rosie Stephenson-Goodknight.

Earwig’s wing inspires compact designs that fold themselves (via). Interesting use of metastability to form shapes that fold down to small sizes and hold their rigidity when unfolded. Also with mini-rant about how badly chosen the authors’ term “4d printing” is.

Perverse incentives in academia (G+). Goodheart’s law tells us that numerical measures of quality quickly become corrupted, but this table describes more specifically what has gone wrong with standard ways of comparing academic productivity.

Baiocchi figures for Besźel polycubes. How can we glue together copies of a given polycube, using only cubical cells with at least two even coordinates, to form a bigger shape with the symmetry of a cube? A a small corner of an extensive set of pages on polyforms by Colonel George Sicherman.