Flip graphs of matroids are expanders: gilkalai.wordpress.com/2018/12
Gil Kalai reports on a new proof by Nima Anari, Kuikui Liu, Shayan Oveis Gharan, and Cynthia Vinzant of a conjecture by Milena Mihail and Umesh Vazirani that any subset \( S \) of at most half of the bases of a matroid has at least \( |S| \) flips to a base outside \( S \).

Based on a preprint at arxiv.org/abs/1811.01816, via plus.google.com/11727145723611

Taylor and Francis doing Trump’s dirty work for him: gowers.wordpress.com/2018/12/0

Timothy Gowers reports on the journal _Dynamical Systems_ refusing to publish a paper (supposedly, arxiv.org/abs/1408.1835) after editorial acceptance because one of its coauthors is Iranian.

New blog post: General-position hypercube projections

In which I look for large general-position subsets of 2d grids (the no-three-in-line problem) by starting with higher-dimensional point sets and then carefully flattening them. So far the results are only computational but they look promising.

Australia's war on encryption: the sweeping new powers rushed into law

With all the vague "end of the internet!" or "why is everyone so upset at such good idea" stories elsewhere on the new Australian backdoor-your-apps law, it's good to see a piece that explains what it actually does.

The moral seems to be: don't allow or agree to any automatic updates while in Australia. Australians, if you want security from govt snooping and from security flaws, tough luck.

ACM announces their 2018 class of fellows: acm.org/media-center/2018/dece
Congratulations, new fellows!

You can also see Wikipedia's coverage of all the ACM fellows at en.wikipedia.org/wiki/List_of_
Quite a few are still missing articles, so if you want to improve Wikipedia's coverage of computer scientists there's still plenty to do.

Rigid Foldability is NP-Hard: arxiv.org/abs/1812.01160

It was previously known that folding a purported origami folding pattern to a flat state is NP-hard, because you can encode logic in the way the paper gets in the way of itself. But this paper proves that it's hard even to tell whether you can make any rigid motion at all starting from completely unfolded paper, well before self-interference kicks in. Instead, the difficulty involves getting sums of angles to come out right.

How to make a hollow geodesic plywood ball

I don't actually care about the how-to part of the linked video, but the malachite-like patterns that emerge from the plywood layers on the resulting ball are quite pretty. If you think about it, it's reversed from actual malachite, where the 3d structure involves nested spheres, and you get the patterns from a flat cut. Here, the 3d structure involves flat layers, and you get the patterns from a spherical cut.

New blog post: Triply-Hamiltonian edge colorings

In mathstodon.xyz/@mjd/1010988538, Mark Jason Dominus (@mjd) observed that the regular dodecahedron can have its edges properly colored with three colors so that every two colors form a Hamiltonian cycle. In this post, I survey constructions for more graphs like this, and prove that no planar bipartite graph can have a coloring like this.

The State Court of Berlin has ordered the German-language Wikipedia to remove claims linking CS prof Alex Waibel to US intelligence. "Whether the claims were justified or not was not taken into account by the court" — instead it seems the court disagrees with Wikipedia's policy of repeating claims from published sources, and insists that potentially-harmful claims can only be published by people who have researched them directly.

heise.de/newsticker/meldung/Ur (in German), via en.wikipedia.org/wiki/Wikipedi

Larry Lessig on how "industry influence can affect even the ethically engaged professional" and how this corruption can lead to anti-scientific popular backlashes such as the anti-GMO movement: chronicle.com/article/How-Acad

Choose Your Own Adventure: alisonmarr.com/cyoa.html

Alison Marr and two students visualize the graph structures of choose-your-own-adventure books.

A Collector of Math and Physics Surprises: Tadashi Tokieda discovers new physical phenomena by looking at the everyday world with the eyes of a child

Via plus.google.com/+Quantamagazin

This Is the Way the Paper Crumples: In a ball of paper, scientists discover a landscape of surprising mathematical order

Siobhan Roberts in the NYT writes about Omer Gottesman's discovery that when repeatedly crumpling paper, the total length of the creases is surprisingly predictable. Via twitter.com/bit_player/status/, based on Nature paper at doi.org/10.1038/s42005-018-007

Stories About a "Seagull" (1966)

John Sisson (a friend and librarian here at UCI) has been posting old and mostly-Russian children's books about space travel to his blog, Dreams of Space. This one is about Valentina Tereshkova.

The future of academic freedom and the curious, disturbing case of Derek Pyne:

Unless the story has another side that we haven't heard, it's quite disturbing: Derek Pyne, an econ professor at Thompson Rivers University in Canada, published a peer-reviewed study showing that many of his colleagues had been using predatory publishers, and rather than addressing the issue the campus administrators suspended him and banned him from campus for being a troublemaker.

In case anyone doesn't know about the TCS aggregator (twitter.com/cstheory) it's a useful resource for new theoretical computer science posts as a twitter stream. It's down this week but should soon be back up as its creator Arvind Narayanan hands over the reins to Suresh Venkatasubramanian (cstheory.stackexchange.com/a/4).

While I'm posting about feeds, instructions for obtaining RSS feeds for Mastodon accounts (such as the one I'm moving to from G+) are at mastodon.at/@switchingsocial/1

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