Fun with Algorithms proceedings, now online: drops.dagstuhl.de/opus/portals

So if you want to read about robot bamboo trimmers, phase transitions in the mine density of minesweeper, applications of the Blaschke–Lebesgue inequality to the game of battleship, multiplication of base-Fibonacci numbers, or trains that can jump gaps in their tracks, you know where to go.

The conference itself has been rescheduled to next May. Maybe by then we can actually get a trip to an Italian resort island out of it.

Looking it up it appears so — the story is that London got it from earlier American hip-hop

Dynamic graph planarity testing, in Quanta: quantamagazine.org/a-new-algor

Original papers from SODA 2020, early this year: arxiv.org/abs/1910.09005 and from STOC 2020: arxiv.org/abs/1911.03449

Origametry: Mathematical Methods in Paper Folding (cambridge.org/us/academic/subj), new book coming out October 31 by @tomhull

I haven't seen anything more than the blurb linked here and the limited preview on Google Books (books.google.com/books?id=LdX7), but it looks interesting and worth waiting for.

Trump officials are now telling their supporters to buy guns and ammunition to use against scientists for being anti-Trump. No, seriously: nytimes.com/2020/09/14/us/capu thehill.com/policy/healthcare/

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New Combinatorics journal to watch

math.sfsu.edu/beck/ct/board.ph

Intended to be a successor to JCTA. I hope they sort out a TLS certificate soon.

A prickly structure made of 70,000 reusable hexapod particles: thisiscolossal.com/2018/10/a-p

Sort of like those seawalls they build by jumbling together giant concrete caltrops, only with pieces that are not quite so big and with usable spaces left void within it. Sometimes the article says "hexapod" and sometimes "decapod"; the pictures appear to show structures that mix two different kinds of particle.

Open is not forever: a study of vanished open access journals, arxiv.org/abs/2008.11933

This study shows the need for systematic archiving and redundant copying of online open journals, but I suspect that the problem for small hand-run print-based journals without much library pickup might be much worse. Via news.ycombinator.com/item?id=2 and sciencemag.org/news/2020/09/do

The hexagon-minimizing simple bipartite polyhedra of my recent blog post 11011110.github.io/blog/2020/0 make nice shapes when converted to simple orthogonal polyhedra (see arxiv.org/abs/0912.0537): a squared-off amphitheater with L-shaped terraces of increasing length as they rise, or a diagonal staircase with congruent L-shaped steps. In each case the outer $$2n$$-gon is the underside of the polygon and the inner cycles are the horizontal faces.

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Rod Bogart's twitter feed is a blast. Here's his tweet announcing that he's made an hourglass that demonstrates Archimedes’ theorem that the volume of a cylinder is the sum of the volumes of its inscribed sphere and cone: twitter.com/RodBogart/status/4

Peter Cameron gives a nice roundup of two recent online conferences on group theory and combinatorics that he attended more-or-less simultaneously (something that would have been impossible for physical conferences): cameroncounts.wordpress.com/20

The parts on synchronizing automata and twin-width particularly caught my attention as stuff I should look up and find out more about.

New blog post: Eberhard's theorem for bipartite polyhedra with one big face, 11011110.github.io/blog/2020/0

Or, if you want to build a simple polyhedron given one $$2n$$-gon face and a fixed number of quadrilaterals, but an unlimited number of hexagons, what's the fewest hexagons you need to use?

Early Renaissance painter Piero della Francesca was also an accomplished mathematician, and his book on polyhedra, De quinque corporibus regularibus (new Wikipedia article en.wikipedia.org/wiki/De_quinq) has an interesting history that deserves to be better known. Rediscovery of the mathematics of Archimedes! "First full-blown case of plagiarism in the history of mathematics" (by Luca Pacioli, in Divina proportione)! Maybe owned by John Dee! Long lost and found centuries later in the Vatican Library!

Flamebait post of the day: Why mathematicians should stop naming things after each other, nautil.us/issue/89/the-dark-si

Via news.ycombinator.com/item?id=2 where for once the discussion is worth reading (main point: the alternative, using common English words to describe specialized technical concepts, can be even more confusing).

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Ideal polyhedron (en.wikipedia.org/wiki/Ideal_po), a polyhedron in hyperbolic space with all vertices at infinity

Sylvester–Gallai theorem (en.wikipedia.org/wiki/Sylveste), that every finite set of points in the Euclidean plane has a line that either passes through all of them or through exactly two of them

Both newly promoted to Good Article status on Wikipedia.

Lorenz Stöer's geometric landscapes: blog.graphicine.com/lorenz-sto

In 2014 I linked a different page with a few of Stöer's 16th-century proto-surrealist combinations of landscape and geometry, but they were black and white. This one has more of them, in color.

New blog post: Isosceles polyhedra, 11011110.github.io/blog/2020/0
based on a new preprint: On Polyhedral Realization with Isosceles Triangles, arxiv.org/abs/2009.00116

Closed quasigeodesics on the dodecahedron (quantamagazine.org/mathematici), paths that start at a vertex and go straight across each edge until coming back to the same vertex from the other side. Original paper: arxiv.org/abs/1811.04131, doi.org/10.1080/10586458.2020.

I saw this on Numberphile a few months back (video linked in article) but now it's on _Quanta_.

The Graph Drawing 2020 program is online: gd2020.cs.ubc.ca/program-no-li

It is September 16-18, from 8AM to noon Pacific daylight time (the time in Vancouver, where the conference was originally to be held). The format has talk videos available pre-conference, with sessions consisting of 1-minute reminders of each talk and 5 minutes of live questions per talk. Jeff Erickson and Sheelagh Carpendale will give live invited talks.

It's free but requires registration, deadline September 10.