Linkage

Ok, some of these are not so much links as mini-reports from SPAA/STOC/FCRC. For an actual conference report, see Lance’s post.

• Squaring the spherical earth (\(\mathbb{M}\)). For surveying purposes, Orange County is divided into “sections”, typically one square mile (not axis-aligned!) with small brass markers at their corners. One corner lands in the UCI faculty housing development where I live, and the housing association took the opportunity to make a larger decorative marker for it.

• Integer linear programming, change-making, and Presburger arithmetic (\(\mathbb{M}\)). Integer arithmetic problems with a constant number of variables and one level of quantifiers (example: given a constant number of coin types, find the largest amount of money for which you cannot make change) have long been known to be polynomially solvable, but in FOCS 2017 Nguyen and Pak proved that only two levels of quantifiers make the problem hard.

• Dots and triangles (\(\mathbb{M}\)). Online variant of dots and boxes by Tomas Rikicki.

• University of Strathclyde proposes to axe combinatorics and their three strong combinatorics faculty members (\(\mathbb{M}\), via). This comes despite the group being both strong in research and important in undergraduate education. The apparent cause is Strathclyde’s placement of combinatorics in computer science rather than in mathematics and in their use of standards aimed more at computer science than mathematics (like bringing in large grants). There’s an online petition against the cuts closing very soon: 5pm British time, July 1.

• Catherine Greenhill is setting up a new network for women in combinatorics, meaning “anyone who identifies as a woman, is non-binary, two-spirit, or gender diverse” (\(\mathbb{M}\)). Their website currently only has a sign-up form, but expect more to come.

• Slides from three of my recent conference talks (\(\mathbb{M}\)): Cubic planar graphs that cannot be drawn on few lines; Counting polygon triangulations is hard; NC algorithms for perfect matching and maximum flow in one-crossing-minor-free graphs.

• Certain conference speakers need to be told that using sans-serif ∑ for one central notation and sans-serif bold ∑ for a different central notation is a bad idea. That decorating both of them by the same subscripts and the same hats doesn’t help. And that when someone asks for clarification of the notation, answering with “We should move on…this is a thing you can compute on your own” rather than actually explaining is rude (\(\mathbb{M}\)).

• The STOC Wikipedia edit-a-thon was called off because the convention center was locked up and participants couldn’t get into the room it was scheduled for (\(\mathbb{M}\)). But it was successfully rescheduled for the next day, unfortunately too late in the conference for me to participate.

  In other news from STOC, spammy journal publishers have found a new way to spam us: fund student authors with travel awards (laudable and non-spammy!) but then require the student presenters to display a whole slide of advertising for the journal by way of acknowledgements (spammy!).

• xkcd on reading Wikipedia in the original Greek (\(\mathbb{M}\)).

• Discrete logarithms in quasi-polynomial time in finite fields of fixed characteristic (\(\mathbb{M}\)). New preprint by Kleinjung and Weselowski.

• Short video on interleaving multiple copies of the infinite Laves graph (\(\mathbb{M}\)). Sound not necessary.

• Two new papers explore the complicated physics behind bubbles and foams (\(\mathbb{M}\)). Juanes et al find universality in pinching off uniformly sized bubbles from a tube much like drops from a dripping faucet. And Yanagisawa and Kurita discover two mechanisms for breaking bubbles to propagate through a foam. As it contracts, the breaking bubble can hit other bubbles, and it can also scatter off droplets which hit other bubbles.

• Centrality analysis of Wikipedia links between mathematicians (\(\mathbb{M}\), via). None of the names listed are surprising, but the ordering might be a little. Noether makes the top 10; Bourbaki, Grothendieck, and Turing are farther down. Martin Gardner makes the cut (barely), at #35.