Linkage

Turkey has charged over 700 academics with terrorism for signing a peace petition (\(\mathbb{M}\)). Among the most severely penalized is Tuna Altınel, a mathematician in France who was arrested visiting family in Turkey, and who has now been imprisoned for over 50 days (via).

László Lovász’s book “Graphs and Geometry”, on geometric representations of graphs (\(\mathbb{M}\), via). The print version should appear in a month or so from the AMS.

University of Alaska budget gutted by 40% (\(\mathbb{M}\), see also). The total amount cut over the past five years (including this new biggest cut) is more like 63%, from $522M to $192M. And the likely response is to close one of its three main campuses and all 13 smaller community campuses. Ironically, the cause is rightwing insistence on a universal basic income of $3000/person from fuel extraction revenues.

The annual Big Internet Mathoff — view and vote on your favorites! (\(\mathbb{M}\)). The first few matches include commutativity of logexponentiation vs weather infovis, the geometry of the Sydney Opera House vs straight lines on a donut, multiplication tables and muffins and a video on shapes in La Sagrada Familia (shot on location?!) vs an introduction to fractals. More daily for roughly a month.

Chinese scientists guilty of “researching while Asian” in Trump’s America (\(\mathbb{M}\), via, see also). The story focuses on star cancer researcher Xifeng Wu, forced to resign from the University of Texas, apparently because she fostered collaboration with Chinese cancer research institutions at the behest of her higher administration.

Chris Purcell thinks about graphs with degree sequence \(1,3,3,3,\dots\). They have to have at least one cycle of each parity.

A formula for designing lenses with no spherical aberration (\(\mathbb{M}\), via). This seems to have little practical value as there was already a numerical solution, and I don’t think it handles chromatic aberration, but it’s interesting that there is an analytic formula for these shapes.

Last week I traveled to Milan for the Symposium on Geometry Processing (\(\mathbb{M}\)). They also have an official twitter stream, mostly consisting of event photos. The sightseeing highlight of my trip was seeing pages of Da Vinci’s Codex Atlanticus at the Ambrosian Library.

Evoboxx (\(\mathbb{M}\)), a retrostyled portable device that does only two things: run Conway’s Game of Life and generate sounds from it. Not very practical in these days of cell phones but then maybe that’s what makes it a fun project.

Modal model theory (\(\mathbb{M}\)). For graphs, this extends first order logic (where the only quantification is over vertices and the only predicate is adjacency) with operators \(\Diamond\) and \(\Box\). \(\Box(F)\) is true when all supergraphs model \(F\) and \(\Diamond(F)\) is true when at least one supergraph models \(F\). This can express nontrivial graph properties like \(k\)colorability, and comes in two variants depending on whether you can quantify outside the operators.

Very quick video tutorial on how to make the Miuraori fold, by Polly Verity (\(\mathbb{M}\), via).

Trávník’s smooth selfreferential formula (\(\mathbb{M}\), via). It is actually a linked set of formulas, described in a typeset image, that when plotted as described in the image produces the image itself. It follows the same ideas as earlier selfreferential formulas like Tupper’s selfreferential formula but unlike them describes a smooth vector image based on splines instead of a pixelated bitmap.

Leiden wall formulas (\(\mathbb{M}\)). The last time I was in Leiden they were decorating the exterior walls of all their buildings with poems of many different languages. Now they’ve moved on to the language of mathematics.

Numberphile video on Dehn invariants (15minutes; \(\mathbb{M}\)). The Dehn invariant is a value derived from a polyhedron that doesn’t change if you cut up the polyhedron into smaller polyhedral pieces and rearrange them into a different polyhedron. It’s 0 for the cube and nonzero for other Platonic solids, proving that they can’t be cut and rearranged into a cube. See the Wikipedia article for more technical details.