April 01, 2015

3:56 AM | Linkage
Non-uniformly-random playlists sound more random than random ones (G+)Is it a good thing that science is monolingual? Is it even true? (G+)Bringing Wikipedia to a school without electricity (G+)Erik Demaine presents the MAA Centennial Lecture (G+)What if we held elimination tournaments based on the strength of math departments? (G+)Mathematical equations as architectonic forms (G+)Persi Diaconis on good and bad ways to shuffle cards (G+)Open problems in topological graph theory from the late […]

March 22, 2015

5:18 AM | Clique minors in de Bruijn graphs
In my new Wikipedia article on the queue number of graphs, the binary de Bruijn graphs form an important family of examples. These are 4-regular graphs with one vertex for every n-bit binary string, and with an edge from every string of the form 0s or 1s to s0 or s1. I posted about them here several years ago, with the following drawing, which can be interpreted as a 2-queue drawing with one queue for the edges that wrap around the left side and another for the edges that wrap around the […]

March 21, 2015

4:55 AM | Shattered glass
A broken pane in the main stairwell of my department's building (maybe a bird strike?) gave me a chance to play with the geometry of shattered glass.( The rest of the photos )

March 16, 2015

1:11 AM | Linkage for the ides of March
The Schmidt arrangement, triangular rosettes of circles from number theory (G+)Brückner, Vielecke und Vielflache (1900), with a tumblr post of some stellated polyhedra photographed in the book (G+)$1000 prize for solving open problems in OEIS (G+)MAA celebrates Women's History Month (G+)Tensegrity robot video (G+)Mini-biographies of five women scientists (G+)Numberphile video on the diversity of human natural-language number systems (G+)Interactive 3d fractal fly-through (G+)Yet more […]

March 15, 2015

4:31 AM | Photos from Bellairs
I was in Barbados last week for the Third Annual Workshop on Geometry and Graphs. This time, unlike my visit last year, I remembered to bring my camera.( Many more photos, not all by me )

March 06, 2015

6:46 AM | The nearest neighbor in an antimatroid
Franz Brandenburg, Andreas Gleißner, and Andreas Hofmeier have a 2013 paper that considers the following problem: given a finite partial order P and a permutation π of the same set, find the nearest neighbor to π among the linear extensions of P. Here "nearest" means minimizing the Kendall tau distance (number of inversions) between π and the chosen linear extension. Or, to put it another way: you are given a directed acyclic graph whose vertices are tagged with distinct numbers, […]
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