- Sexism and bureaucracy at Wikipedia and an update on the Walter Lewin sexual harassment story (G+)
- Wisconsin gov. Walker seeks major cuts on universities so he can build a sportsball facility; Calif. gov. Brown isn't much better (G+)
- Conference search: Theory (G+)
- Automated textual image analysis results and engine (G+)
- Super eggs: the mathematics behind the shape of, among other things, Azteca Stadium in Mexico City (G+)
- Cal State Univ. gives up on Wiley journals after hefty price increases and refusal to unbundle (G+)
- Topological Tverberg counterexample. It is true for all prime-power dimensions but that wasn't good enough to be true for all dimensions. (G+)
- Randomly cut and flipped rectangles from another Tumblr of interesting mathematical visualizations (G+)
- 1961 interview with F1 racing driver Bruce McLaren's family. From my mother's blog; McLaren was her second cousin. (G+)
- Muslim rule and compass: the magic of Islamic geometric design (G+)
- UMass Amherst bans Iranian STEM grad students (G+)
- Many links on pop-up books and related paper engineering problems (G+)
- SoCG accepted papers, with abstracts (G+)
- The Nymwars continue at Facebook (G+)

The three most obvious choices for me are DBLP, ACM Digital Library, or MathSciNet.

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- ... that Bernard Chazelle's son directed a film that has been nominated for a best-picture Oscar? (G+)
- ... that the rebellion in Ukraine has caused many scientists and whole universities to move? (G+)
- ... that there have been many recent papers on counting geometric incidences? (G+)
- ... that the shape of a piece of 3d-printed chocolate might influence its flavor? (G+)
- ... that placing precise slits in a flat paper surface can cause it to curve in predictable ways? (G+)
- ... that the waterbear is a new fast knightship in Conway's game of life? (G+)
- ... that Richard Sweeney's paper-folding artworks are inspired by snow and clouds? (G+)
- ... that Google has a service for checking whether your home page is mobile-friendly? (G+)
- ... that the sum of the first n squares is n(n+1)(2n+1)/6? (G+)
- ... that epicycles can be visualized by spheres spinning inside each other? (G+)
- ... that Paul Erdős traveled to Madras to meet Krishnaswami Alladi when Alladi was only an undergraduate? (G+)
- ... that you can persuade bees to make honeycombs in nonstandard tessellations by giving them patterned foundation plates? (G+)
- ... that professors used to send each other postcards requesting printed copies of their recent papers? (G+)
- ... that you can fold a dollar bill into a fish? (G+)
- ... that Theo Jansen's autonomous walking creatures have no brains? (G+)

*Approximation Algorithms*book chapter-by-chapter, and learning lots of interesting material that I didn't already know myself in the process.

One of the things I recently learned (in covering chapter 6 on feedback vertex set approximation)

^{*}is that, although all the students have taken some form of linear algebra, many of them have never seen a vector space in which the base field is not the real numbers or in which the elements of the vector space are not tuples of real coordinates. So instead of discussing the details of that algorithm I ended up spending much of the lecture reviewing the theory of binary vector spaces. These are very important in algebraic graph theory, so I thought it might be helpful to write a very gentle introduction to this material here.

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- Real-time 3d special effects in modern dance (G+)
- How not to react to conference talks that happen to be presented by women (G+, including also an unrelated report from the SODA business meeting)
- Photos of icy landscapes showing how varied the geometry of ice can be (G+)
- New ACM fellows (G+)
- n-body choreagraphies (strange solutions to the n-body problem in which all bodies follow each other along a curve; more and still more; G+)
- Men (on the Internet) don’t believe sexism is a problem in science, even when they see evidence (G+)
- The fractional chromatic number of the plane (G+)
- Elwyn Berlekamp video on dots-and-boxes strategy (G+ reshare)
- Richard Elwes sings the Grothendieck Song for us (G+)
- Animated shapes from a 3d printed object, a turntable, and a strobe light (G+ reshare)
- Why tilings by regular polygons can't include the pentagon (G+ via MF)

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The 12 circular arcs of this diagram correspond to the 12 vertices of a cuboctahedron, and the 24 contact points between arcs (the points where one arc ends as it runs into another arc) correspond to the 24 edges of the cuboctahedron. What we want to know is which other graphs can be represented like the cuboctahedron in this way? They have to be planar, and every subgraph has to have at most twice as many edges as vertices (because every set of arcs has twice as many endpoints as arcs) and beyond that it's a little mysterious. But we have some natural subclasses of the planar graphs for which we can prove that such a representation always exists (for instance the 4-regular planar graphs) and some NP-hardness results.

Two other uploads of possible interest: my report as co-PC-chair at the ALENEX business meeting, and my talk on Miura folding (both with small corrections to the slides I actually used). I've posted here before about the Miura folding results. For the ALENEX report, besides the usual breakdown of acceptance rates and subtopics, there were two more substantial issues for future planning: should ALENEX move its submission deadline earlier than the SODA notification date (so that the PC has adequate time to review the submissions), and should it accept more papers? The sentiment at the meeting seemed to be in favor of both ideas.

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- Pseudonyms are used mostly for privacy, not trolling (G+)
- Attacks on the peer review system including authorship for sale, false refereeing, plagiarism, etc (the G+ post includes several more links)
- Randomly generated polygonal insects (G+)
- Qu-ant reversible cellular automata (G+ reshare)
- Sonobe unit polyhedra, modular polyhedra as Christmas decorations (G+ reshare)
- Domino chain reaction video demonstrating exponential scaling in energy amplification (G+)
- The adventitious angle puzzle for the advent season (G+)
- The Gauss Christmath Special video (G+)
- Collections of graph theory open problems (G+)
- Knuth's dragon-curve mistake video (G+ reshare)
- One million arXiv preprints (G+)
- Origami batteries (G+)

The rest of the gallery.

It's normal for there to be no cell phone service at my parents' house in Mendocino. Cell phones finally reached downtown Mendocino a couple of years ago over the objections of some protesters who were terrified of being exposed to any form of electromagnetic radiation, but there's a hill between downtown and the house that blocks the signal. There would normally be landline phone service there, but the lines got flooded in the big storm a couple of weeks ago and AT&T hasn't succeeded in drying them out yet. And my parents also have cable internet, but for some other reason that went down too. So we had to resort to old-fashioned behavior like reading books or actually interacting with each other instead of all being absorbed in our own separate electronic devices the way we otherwise would likely have been.

When this happens, we can use it to construct a nice two-dimensional grid representation of the polytope.

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*k*-best enumeration algorithms for the Springer

*Encyclopedia of Algorithms*, I wrote a first draft before checking the formatting requirements. It ended up being approximately five pages of text and seven more pages of references, and I knew I would have to cut some of that. But then I did check the format, and saw that it needed to be much shorter, approximately two pages of text and a dozen references. I don't regret doing it this way; I think having a longer version to cut down helped me to organize the results and figure out which parts were important. But then I thought: why not make the long(er) version available too? I added a few more references, so now it's about six pages of text and ten of references, still closer to an annotated bibliography than an in-depth survey. Here it is: arXiv:1412.5075.

- The number theory behind why you can't have both perfect fifths and perfect octaves on a piano keyboard (with bonus lattice quotient music theory link; G+)
- Sad news of Rudolf Halin's death (G+)
- Frankenstein vs The Glider Gun video (G+)
- Günter Ziegler on Dürer's solid (WP; MF; G+)
- Nature will make its articles back to 1869 free to share online, for certain values of "free" that you might or might not agree with (G+)
- Albert Carpenter's polyhedron models (G+)
- The only complete proof from Fermat and the gaps in arithmetic progressions of squares (G+)
- Mark-Jason Dominus on how and why he negotiated with his book publishers to be able to keep a free online copy of his Perl book (G+)
- Video on drawing mushrooms with sound waves (G+)
- Senate staffer tries to scrub "torture" reference from Wikipedia's CIA torture article (G+)
- Numberphile video on origami angle trisection (G+)
- Video on the world's roundest object and why it was made (G+)
- How much text re-use is too much? A statistical study of plagiarism on arXiv (via; G+)

The surface of a three-dimensional polyhedron is a two-dimensional space that's topologically equivalent to the sphere. By the Jordan curve theorem, every cycle of edges and vertices in this space cuts the surface into two topological disks. But the surface of a four-dimensional polytope is a three-dimensional space that's topologically equivalent to the hypersphere, or to three-dimensional Euclidean space completed by adding one point at infinity. So, just as in conventional Euclidean space, polygonal chains (such as the cycles of edges and vertices of the polytope) can be nontrivially knotted or linked. If so, this can also be seen in three-dimensions, as a knot or link in the Schlegel diagram of the polytope (a subdivision of a convex polyhedron into smaller convex polyhedra). Does this happen for actual 4-polytopes? Yes! Actually, it's pretty ubiquitous among them.

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- Gamergate's attackers move on from (female) indie game developers to (female) game researchers (G+)
- Scammy publisher uses your name as the author of fake papers (G+)
- Escher-like impossible figures by Regalo Bizzi based on a triangular grid (G+)
- James Turrell installation in Las Vegas (G+)
- Waiting for Godot: The Game (by Zoe Quinn; G+)
- Fedorov's Five Parallelohedra, a complete classification of the shapes that can tile space by translation (G+)
- On the high variance in journalistic standards for plagiarism (G+)
- How many median graphs are there? (G+)
- SODA/ALENEX/ANALCO 2015 preregistration closes Monday, Dec. 1 (G+)

(G+)- Hexagonal diamond, a crystalline carbon structure even harder than true diamond (G+)
- The Laves graph, an infinite symmetric 3-regular graph that forms yet another possible carbon crystal (G+)

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