The Spring term just ended at UCI (we’re on a quarter system, so we run later into June and then start up again later in September than most other US universities). I haven’t yet turned in my grades, but I can already feel summer setting in.

• Mir Books ($$\mathbb{M}$$, via). A big collection of interesting-looking Soviet-era mathematics and science books and booklets, translated into English and free to read.

• Chip-firing games and sesquinary notation ($$\mathbb{M}$$). Jim Propp writes a monthly long-form math blog and somehow I hadn’t encountered it before; this is one of its many interesting entries. One of the oddities about base $$3/2$$ is that you calculate it bottom-up (by starting from a ones digit that’s too big and then carrying things higher) instead of top-down (by greedily subtracting powers).

• A discussion on whether proofs in Wikipedia articles need references, and what those references are for.

• The tale of Horgan’s surface ($$\mathbb{M}$$, via, see also, see also), a nonexistent minimal surface whose existence was incorrectly predicted by numerical experiments, named sarcastically after a journalist who incautiously suggested that proof was a dead concept.

• Compact packings of the plane with three sizes of discs ($$\mathbb{M}$$), Thomas Fernique, Amir Hashemi, and Olga Sizova. Here, “compact packing” means interior-disjoint disks forming only 3-sided gaps. The circle packing theorem constructs these for any finite maximal planar graph, with little control over disk size. Instead this paper seeks packings of the whole plane by infinitely many disks, with few sizes. 9 pairs of sizes and 164 triples work.

• Luca Trevisan posts a series of tutorials on online convex optimization, where you want to approximately minimize a sequence of convex functions before discovering what the functions are (parts $$-1$$, $$0$$, $$1$$, $$2$$, $$3$$, $$4$$, $$5$$; $$\mathbb{M}$$). It’s a hot topic in TCS with connections to regularity lemmas, fast SDP approximation, and spectral sparsifiers.

• Squared patterns of ocean waves ($$\mathbb{M}$$), and wave patterns in social media: search for “cross sea” and note its appearance on gizmodo in 2014, amusingplanet in 2015, azula in 2017, providr in 2018, sciencealert in 2019…all repeating the same somewhat garbled explanation of mathematical wave models and danger to shipping.

• The SIGACT Committee for the Advancement of Theoretical Computer Science is planning a Wikipedia edit-a-thon, in Phoenix on June 24 as part of STOC ($$\mathbb{M}$$). You can help, and you don’t even have to brave the desert heat to do so! There’s a shared spreadsheet where CATCS is crowdsourcing TCS topics on Wikipedia that need help. Add your favorite missing algorithm, theorem, complexity class, etc, and it’s likely it’ll get some attention.

• While I’m publicizing activities associated with STOC and FCRC next week in Phoenix, here’s another: the TCS Women Spotlight Workshop ($$\mathbb{M}$$). It features an inspirational talk from Ronitt Rubinfeld (in my experience a great speaker), four “rising star” talks by Naama Ben-David, Debarati Das, Andrea Lincoln, and Oxana Poburinnaya, a panel/lunch for women at STOC, and a poster session of recent theoretical computer science research by women.

• Two colleagues from my department, Alex Nicolau and Alex Veidenbaum, are participating in a Venice Biennale project ($$\mathbb{M}$$) in which viewers converse with computerized simulations of poet Paul Celan and politician Nicolae Ceaușescu. The Alexes usually work on the more technical side of CS (parallelizing compilers, computer architecture, and embedded systems) so it’s interesting to me to see this softer direction from them.