2026-07-05T08:21:40Z https://njump.me robinhouston https://njump.me/npub13dp7zd8dvmkvmdkwhzktavq6vxee4kztkmsdkxtj86wtrhnfae9sn5f0qj https://media.mathstodon.xyz/accounts/avatars/109/132/739/246/229/143/original/47477125549a073f.jpeg https://media.mathstodon.xyz/accounts/avatars/109/132/739/246/229/143/original/47477125549a073f.jpeg https://njump.me/nevent1qqsyn63ge46cnvsq88k5nfcauvurs9sh2hstgaawyz7wty45hv8pryqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykzs9hqc There’s a fun paper showing that you can define all elementary functions using just two primitive operations: the constant 1, and the binary function eml(x, y) := e^x - log(y).<br/><br/><a href="https://arxiv.org/abs/2603.21852">https://arxiv.org/abs/2603.21852</a><br/><br/>That’s a neat little result, which makes for some fun games.<br/><br/>What’s the simplest expression you can find that evaluates to your favourite constant?<br/><br/>The best I have found for 2 is:<br/><br/>eml(1, eml(eml(eml(1, eml(eml(1, eml(1, eml(1, 1))), 1)), eml(1, 1)), 1)) 2026-04-15T21:30:26Z https://njump.me/nevent1qqszphss2lnm404tsszjndtm3ruy0nrlzj33hfcasycad4gdvhwgp7qzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykrfdkar In reply to <a href='/nevent1qqsteucv80lznkg3qm2elsld3cvqgu83ahjr8qa20dtm6jvchlpa86ctqd877'>nevent1q…d877</a><br/>_________________________<br/><br/>I am sorry for your loss. 2026-03-26T13:55:33Z https://njump.me/nevent1qqsyg8xmw3kaftg0fvvpnwfugv8zrq7kyzfsy3krguzdzfpupk5sskczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk3glmgt TIL. In April 1974, in the middle of the night, a small group of conspirators secretly installed a large tensegrity icosahedron made from discarded telephone poles on the campus of Twente University in the Netherlands.<br/><br/>It’s still there. People call it Het Ding (“the thing”).<br/><br/><a href="https://www.utwente.nl/en/alumni/inspiring-alumni/ut-canon/stories/het-ding/">https://www.utwente.nl/en/alumni/inspiring-alumni/ut-canon/stories/het-ding/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/116/210/792/392/176/399/original/fcf8215535988335.png"> <br/> 2026-03-11T13:37:14Z https://njump.me/nevent1qqsfexvpv6l58f4zstdavfpa6r8rs5xzvfdwa7e5uh6dy9mtqs0268gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykrwsc5q In reply to <a href='/nevent1qqs9x4klk9t6rrtn0z0s2s4emjyym3ewjhgqw48pq8wuyh8kftyperqk3aps6'>nevent1q…aps6</a><br/>_________________________<br/><br/>Thanks. I do like videos. I&#39;ve just finished watching the first one, which was great. 2026-01-04T13:18:47Z https://njump.me/nevent1qqs980svrqljx7ejscm5mwd3qccu72lu689evk7wks93xglctj0x53qzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykaam4k9 In reply to <a href='/nevent1qqsy9nxtncxpadexaucuqrnd4dlrce9m8jg4ujnxkc4j74c3atp55wszc5nrj'>nevent1q…5nrj</a><br/>_________________________<br/><br/>I&#39;m ok with a “bring your own motivation” text in this case, because I already know why I want to understand this theory, and I just need someone who already understands it to lay it out carefully and correctly. But I will check out your lectures too! 2026-01-04T11:45:12Z https://njump.me/nevent1qqsdz927kwxrsk4fctj6c3wn403lg4mglqmm39sx62pap9urw4nc6pczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyks4qj7s In reply to <a href='/nevent1qqsg0wfyu8p6uwjpnaunmnqn3lxh8wst9juep483404r4l7hsdxu2lgxgpg70'>nevent1q…pg70</a><br/>_________________________<br/><br/>It’s a subject I know less about than I feel I ought to, which means I always feel vaguely guilty when it comes up. I am hoping a careful study of the book will correct that. 2026-01-04T01:27:08Z https://njump.me/nevent1qqsqqa8ar79jmja9wlwwh3kclhgjzfh0au4hyh6zr5nhl0zwr0eswsqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykhpdzuy Imagine reading this if you didn&#39;t know what a reflection was.<br/><br/>(This is not a criticism, just a thought that amused me.)<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/833/978/068/192/133/original/f36e7103c7a6e9ae.jpeg"> <br/> 2026-01-04T00:31:25Z https://njump.me/nevent1qqsd08gxuceg0l20cupud9zmr457nvzka73qesw2f6uyyv2d6wctuegzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykjh733s In reply to <a href='/nevent1qqs8q36pah0aj989mxrlxqzww52evz68vc2n8zcqr3s4qe4dg5supaq0tchjl'>nevent1q…chjl</a><br/>_________________________<br/><br/>If multiplication is commutative for the numbers in your matrices, then you can do it in 21 multiplications according to <a href="https://arxiv.org/abs/1904.07683">https://arxiv.org/abs/1904.07683</a> 2026-01-01T22:15:33Z https://njump.me/nevent1qqsgp9cultv4ugm33kadfw28capaf4t6uy3e2ju3vjyelp63zufxuxszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyksk6mzk A 58-Addition, Rank-23 Scheme for General 3x3 Matrix Multiplication <a href="https://arxiv.org/abs/2512.21980">https://arxiv.org/abs/2512.21980</a><br/><br/>I love this sort of explicit work. The algorithm fits in a screenshot:<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/821/133/411/739/410/original/c055f538bf5623a5.jpeg"> <br/> 2026-01-01T17:57:45Z https://njump.me/nevent1qqsf5j6m6xmlpcnuqxpvld0c9agvwyq0p8h5ljf4qmyy9m2hdchfsrqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk58fp5s A lovely new video from <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub10zcfmh333hf5phqzjwn2avyueg2aly69rauj2c5utdg5y6fggv9svdtds5" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Henry Segerman</span> (<span class="italic">npub10zc…tds5</span>)</a></span>: <a href="https://youtu.be/NEJZlGuWGV8">https://youtu.be/NEJZlGuWGV8</a><br/><br/>Stunning photography, as well as a fascinating mechanism. 2025-12-30T15:53:49Z https://njump.me/nevent1qqs8hh7x2rwcyds7la2aku9yn6a0nstqmgu0s7jypctpdmy9w95sqjqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykfzsz2h In reply to <a href='/nevent1qqs03myytqy5hvmjk9fpwuzaq4zhcjm98yn7v2hr98fd68ycwlkg0mqpenkeu'>nevent1q…nkeu</a><br/>_________________________<br/><br/>That&#39;s only accessible to members of the University of Edinburgh; at least I _think_ that&#39;s what the error message is trying to tell me.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/764/483/063/710/864/original/45a2e41072ebb212.jpeg"> <br/> 2025-12-22T17:50:50Z https://njump.me/nevent1qqsdncdzgpr8023zefdkhwhyunvdutv2m3vz3clxw73d6dlhzw0rr9szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykpfmnhg At last I have achieved my ambition of making all the stellations of the rhombic dodecahedron from my blocks<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/763/314/793/743/421/original/9234f68f31a805ac.jpeg"> <br/> 2025-12-22T12:54:27Z https://njump.me/nevent1qqsrswd6wldutlvq7xnkt82znwxlq4l0shrp7n8q9uy50jk5vy62c0gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykckxnn3 In reply to <a href='/nevent1qqsd4pnnv27xdys55j6f3ly24c4qhlufcyrd8nktxllxm89dvcv69pg4h7dvt'>nevent1q…7dvt</a><br/>_________________________<br/><br/>Incidentally, that&#39;s how we know that such a spaceship can only move horizontally (i.e. along the line it occupies). Because the linear configuration is symmetrical in the vertical direction, it cannot possibly move vertically. 2025-12-04T10:36:13Z https://njump.me/nevent1qqswalw832fnxx2s386qm0ayetmtmqs6sakxqsu8za0ve2gk4sfpw4szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk7fg3yu In reply to <a href='/nevent1qqswg02nj74kk42dhmughkehr2pf8mdsnef0l0txq6cq3r35euulukc7yntul'>nevent1q…ntul</a><br/>_________________________<br/><br/>Funnily enough it was eating tapioca pudding, and wondering where such a peculiar word might have originated, that led me to this. 2025-12-03T15:11:59Z https://njump.me/nevent1qqsw97mkchkd55xlts8dnlq8vq5uywev660pp9w5c9tm9w70ks3uwmgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykjfggs2 A language I had never heard of till just now turns out to be the origin of the words tapir, toucan, coati, capybara, piranha, jaguar and tapioca.<br/><br/><a href="https://en.wikipedia.org/wiki/Tupi_language">https://en.wikipedia.org/wiki/Tupi_language</a> 2025-12-03T13:29:18Z https://njump.me/nevent1qqspfvpx70j62caqdvj2n55e3hsru8r9eyedr2klfswfj7de65dkd4szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykxtuc88 I would not have guessed this was possible!<br/><br/>Vladan Majerech has found a one-dimensional spaceship in the Game of Life: a pattern just one cell high and 3,707,300,605 cells wide that, after 133,076,755,768 generations (during which it is not confined to the one-dimensional line, of course) recreates the starting pattern but translated two cells to the right.<br/><br/><a href="https://conwaylife.com/forums/viewtopic.php?&amp;p=222136#p222136">https://conwaylife.com/forums/viewtopic.php?&amp;p=222136#p222136</a> 2025-12-03T03:54:22Z https://njump.me/nevent1qqst9dltk4kym20ckl5yvq8xum6mc06ncqhjvexel6wja7k68tkpx4gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykm5gxrj I had a cool experience on Saturday night at MathsJam. Mike Borcherds had brought a pile of 3D-printed puzzles for people to play with; and I recognised one of the puzzles in the pile as one I had designed!<br/><br/>(It was this one: <a href="https://sketchfab.com/3d-models/third-of-a-cube-assemblable-5c3e1b3550cf490b8c34c7aafc85e887">https://sketchfab.com/3d-models/third-of-a-cube-assemblable-5c3e1b3550cf490b8c34c7aafc85e887</a>, which we&#39;ve talked about on here before.) 2025-11-24T10:30:18Z https://njump.me/nevent1qqsqkg3qfl5jga9cydafhxax4fcmdf8gwxcrkwhs3xh6555fzv657lczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk4t9xkk In reply to <a href='/nevent1qqstumxe7a6hmdn4q05fzvf7vtwzxlfh4dc2shxj6eqz8dwd3ndantckx48us'>nevent1q…48us</a><br/>_________________________<br/><br/>I&#39;m missing some context for this conversation, but I was at the talk you&#39;re discussing. The speaker said, IIRC, that the rationale for making credit cards that size has never been made public, but it&#39;s a reasonable guess that it&#39;s not a coincidence that you can fit exactly 4 × 4 on a sheet of foolscap. 2025-11-24T04:46:19Z https://njump.me/nevent1qqsg5fmu223ypt5ew2vayxz85nrtd8p8cg700vpfwp8mvrsjqtfzynczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykv85vks In reply to <a href='/nevent1qqsqawlx7cyn3k93ktuhqwf94an5en3fhn2rrcuyqc6dhqmg8rvq6wsjev0zm'>nevent1q…v0zm</a><br/>_________________________<br/><br/>is the author’s name joe 2025-11-23T20:38:00Z https://njump.me/nevent1qqswcucgqymaqsjfdza8tfflfe7jevwnjc5eg3y6es0en6pw8ll2k6czyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykpn5cay I&#39;m tempted to update the location in my profile to ‘somewhere in Idaho and uncontactable’, but I fear someone would take it literally.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/333/014/267/552/743/original/8772f2960b6f4d9c.jpeg"> <br/> 2025-10-07T13:04:22Z https://njump.me/nevent1qqsxfv0daasyztfu96vwjlyg0g4t3p8mhqzvhj3cf2vqlcc48sl7s7gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykl2mxhm In reply to <a href='/nevent1qqspvm3mnydxl3vgfsqc6p0a6eaz6rk599kxqsuttdnxauv6xmwzyuqh3gp20'>nevent1q…gp20</a><br/>_________________________<br/><br/>Why on earth does this video already have so many low-effort negative comments? How are those people coming across it?<br/><br/>Usually videos like this are only seen by people who are interested in the topic. Is the mighty YouTube algorithm advertising it to random people? Is it linked from some other popular website? 2025-10-03T07:05:16Z https://njump.me/nevent1qqspvm3mnydxl3vgfsqc6p0a6eaz6rk599kxqsuttdnxauv6xmwzyuqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykduhmfa I enjoyed this talk from Kevin Buzzard, _Where is Mathematics Going?_<br/><br/><a href="https://www.youtube.com/watch?v=K5w7VS2sxD0">https://www.youtube.com/watch?v=K5w7VS2sxD0</a> 2025-10-03T06:52:02Z https://njump.me/nevent1qqs9vlpt4wdxw9a0ypt2g8rk5skyf55sr0xrcvezah0rz7ua54nf8mgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk5w4u4j In reply to <a href='/nevent1qqsvp5vk9fug6n3pxty2ew0cttnc53n07qc9npapvgvl65l522zatug540qmd'>nevent1q…0qmd</a><br/>_________________________<br/><br/>See section 3 of <a href="https://arxiv.org/pdf/2307.14769">https://arxiv.org/pdf/2307.14769</a> 2025-09-26T18:16:11Z https://njump.me/nevent1qqs8gwd5z672jfg4mvyfezsrh4umpsyju8y2pwrfka6ztguc8udmg3szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyke98ps6 In reply to <a href='/nevent1qqsxjpalw5tkf70fh3720yjtlf0wtpnd8hafq86m4n6cc2c848susese58rlv'>nevent1q…8rlv</a><br/>_________________________<br/><br/>One of his great-grandsons is Geoffrey Hinton, the ‘Godfather of AI’. 2025-09-25T09:46:50Z https://njump.me/nevent1qqs8exwtt9aljwwpdzgql88jrctsrskkjq90l95t4z53u5p5g59m3egzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk76t8sw I didn&#39;t know about Charles Howard Hinton. Interesting chap! I just discovered him via researching the etymology and origin of the word tesseract. (Turns out it was coined by Hinton, combining Greek words meaning ‘four’ and ‘ray’.)<br/><br/>He married George Boole&#39;s daughter Mary Ellen Boole, with whom he had four children. Unusually, he also married another woman concurrently, as a result of which he spent time in prison for bigamy.<br/><br/><a href="https://en.wikipedia.org/wiki/Charles_Howard_Hinton">https://en.wikipedia.org/wiki/Charles_Howard_Hinton</a> 2025-09-24T18:25:19Z https://njump.me/nevent1qqs9tyyck3wg4l5ygx8nmxqdgp54j6kkvaetf5tw2ehgp35yrudxkzgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykkkm7ln In reply to <a href='/nevent1qqspgg32pgqwgpfcyqjxcpqlzj9ncm6f2fd3356vczt0m72uekpuxegk8fu55'>nevent1q…fu55</a><br/>_________________________<br/><br/>I&#39;m indifferent to the specific behaviour you describe, but I sometimes have text in one app that I want to search for in a different app, and I like being able to do that very easily just by hitting ⌘E / ⌘⇥ / ⌘G. 2025-09-16T08:46:49Z https://njump.me/nevent1qqsvujnjs8ujk9p9nr8nhpg3endnglsl4t29sm8lxwhlvhzx793frwqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykuh5j2z In reply to <a href='/nevent1qqsqtrehh08s7rfdr7lnrzu9p0cdd26zgsjarjvft5fd75cdg5af62gkclnxt'>nevent1q…lnxt</a><br/>_________________________<br/><br/>I like it. It sounds like something an action movie hero might say just before saving the world. 2025-09-04T09:08:15Z https://njump.me/nevent1qqsfy3a0jmlyv4vvjvjm0842ydws8e2k4l6cwmhg7h8caganf38mhzczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk2l3py4 In reply to <a href='/nevent1qqsfw6cqc909cr8vtt3krtqx8lzqxqg2s2x9sf4dh0tcjqt9djytjlqln55cl'>nevent1q…55cl</a><br/>_________________________<br/><br/>That&#39;s the most American thing I&#39;ve ever heard. 2025-09-02T03:17:00Z https://njump.me/nevent1qqsyg9qhln5tefk6cxtul7yvf8pnhejltz7y4gnx0dy7crx85gkxa8czyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykhspcp8 In reply to <a href='/nevent1qqs2w4chcmhkxwdmtl7xcdj02sna2eg5l2tsmck5dv3zap07wgmugqgk4sapd'>nevent1q…sapd</a><br/>_________________________<br/><br/>The paper does talk explicitly about why they crafted a new polyhedron for the proof, even though they still believe the rhombicosidodecahedron to be non-Rupert.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/106/574/176/917/096/original/d6c42fc1cc6deb0a.jpeg"> <br/> 2025-08-28T13:15:53Z https://njump.me/nevent1qqst554eg8sz9p7ej86hah3xuggknl9men7wspkuf5muuy08ayuxyugzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykkue2p3 A very interesting geometric model that Jeannine Mosely presented at MOVES. Sadly I can&#39;t find anything about it online.<br/><br/>It&#39;s a hinged chain, alternating between 12 pentahedra and 12 tetrahedra, that can be folded into either a regular dodecahedron or a rhombic dodecahedron.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/037/853/617/145/763/original/b83a97dd8b2238e1.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/037/875/093/061/148/original/beed22ae5eff34ce.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/037/877/168/582/405/original/022b0802873e0e2e.jpeg"> <br/> 2025-08-16T10:06:53Z https://njump.me/nevent1qqsxtgrnzrtuyaznp6pjzl2w9ekrtwgzd9v8yt3qatry2c7chjcuk3czyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykw5y567 In reply to <a href='/nevent1qqstz87nxnma0qpxz5utndt4nczvp5h4h8napf6auwn5ew7rhjdrd6ckznpd0'>nevent1q…npd0</a><br/>_________________________<br/><br/>Interesting: they all decode ok on my iOS phone. I wonder what&#39;s different.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/037/733/716/846/552/original/c94e02ebade25015.jpeg"> <br/> 2025-08-16T09:30:47Z https://njump.me/nevent1qqsys4sf3uaqcznnumrvyrdhamzpe7jek6gs4uzm7pazs6fxkmltpzgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykqajemh In reply to <a href='/nevent1qqswjr4ptxl5xsa8r8mfk8sjrmwdl0nazhe9ll4p0wwpxhlfpvk3cuc002yz7'>nevent1q…2yz7</a><br/>_________________________<br/><br/>I think he said that he predicted 8 years ago that it would be resolved within 5 years using control theory, which I assume is a reference to <a href="https://arxiv.org/abs/1703.01352">https://arxiv.org/abs/1703.01352</a> 2025-08-11T20:49:10Z https://njump.me/nevent1qqswjr4ptxl5xsa8r8mfk8sjrmwdl0nazhe9ll4p0wwpxhlfpvk3cuczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykred06k In reply to <a href='/nevent1qqsgqsj6gm8pmm9unku72rf0vhdpkyjzn8aatvtf0cu3lpw4v3f4xeqlfa6rz'>nevent1q…a6rz</a><br/>_________________________<br/><br/>No, it&#39;s still open! He did say a little sadly that it has proved harder to resolve than he hoped it would be. 2025-08-11T20:47:32Z https://njump.me/nevent1qqs0pv0ed3sfgn7nctslefmq2fern8asm696zhwus75rachfykejwlszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykjqvrn6 Thomas Hales at MOVES is showing <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub12cuzzqzv8e8y7na77a9zv47mx2v6pec60qs5h7takzmv5p0mw0fsmgd38p" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Greg Egan</span> (<span class="italic">npub12cu…d38p</span>)</a></span>’s animation of Reinhardt&#39;s smoothed octagon from <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1nf4p4rh06z6n6lsvje4txk7eqs23y3hs8vd7nraq6tgwady5qvsqy3nqe4" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>John Carlos Baez</span> (<span class="italic">npub1nf4…nqe4</span>)</a></span>’s blog.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/012/052/042/802/072/original/5d0c7a9216d8a81d.jpeg"> <br/> 2025-08-11T20:39:59Z https://njump.me/nevent1qqst5xx8hues2jdnpveqyy9jftmhxdu3ghj3sfwdxf7mzkzrhmdz93szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykrwp0t9 In reply to <a href='/nevent1qqsggd95ssvel2pmzft82t7t223lldpd79gzaqpaeryu86mvj6s28wswxsgg0'>nevent1q…sgg0</a><br/>_________________________<br/><br/>Here is the promised animation.<br/><video controls width="100%" class="max-h-[90vh] bg-neutral-300 dark:bg-zinc-700"><source src="https://media.mathstodon.xyz/media_attachments/files/114/935/045/341/525/671/original/e46367ee4cbb5057.mp4"></video><br/> 2025-07-29T06:14:38Z https://njump.me/nevent1qqsggd95ssvel2pmzft82t7t223lldpd79gzaqpaeryu86mvj6s28wszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk9jyeqp I’m hoping that it’s actually possible to physically assemble three of *these* into a cube. <a href="https://skfb.ly/pzCW9">https://skfb.ly/pzCW9</a><br/><br/>I don’t currently have the means to physically test this, but it looks plausible in the animation I made, which I’ll attempt to share in a followup post.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/935/022/186/707/699/original/635e73b59414f520.png"> <br/> 2025-07-29T06:09:54Z https://njump.me/nevent1qqs03fzc0zhhsrs9vatk9fpedx6leqxjay2kkaax3hpdk3ex4tkhgkszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykfjrxnt I think it’s at least mildly surprising that three of these can be combined into a cube. <a href="https://skfb.ly/pzByn">https://skfb.ly/pzByn</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/928/889/350/044/732/original/eb09030ea4cad7a2.png"> <br/> 2025-07-28T04:08:51Z https://njump.me/nevent1qqs84fj73vmtws84rg755rgr3s6f39phpw6x6lpav7zgw28w0xqaf8qzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykdm6aqa Oskar van Deventer has a new video where he demonstrates his ‘Bolts Cube’ puzzle: an evolution of the Bolts Loop that we have been talking about, but this time based on an 8-bar linkage.<br/><br/><a href="https://youtu.be/M4xVaBqg-8U">https://youtu.be/M4xVaBqg-8U</a> 2025-07-19T09:39:36Z https://njump.me/nevent1qqsr657z0mdazdvjzapgcep59wc9fejh4jfuyt8atwyz3nlkvfxxa5qzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk304rt4 There’s a nice mathematical question here from Oskar van Deventer: what is the correct shape for the spiral grooves in this puzzle he designed?<br/><br/>(He was forced to use an approximation in the puzzle as made.)<br/><br/><a href="https://www.youtube.com/watch?v=EHqqXBqckjs">https://www.youtube.com/watch?v=EHqqXBqckjs</a><br/><br/>I find it very hard to visualise the motion that’s taking place here! I’d never even heard of Astrolabacus before. 2025-07-14T21:12:38Z https://njump.me/nevent1qqszw5qakqgp4vu45z3v93whmrtcvkxps06xl0shu8xq7qhcgxzqjqgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk06jrhn Having a 3d printer in the house is forcing me to reckon with the question ‘How many dodecahedra do I need, really?’.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/819/728/740/559/883/original/24cdbe2026b06494.jpeg"> <br/> 2025-07-08T21:28:12Z https://njump.me/nevent1qqsxqrca0z9y230ynypm065cqcmy3g9rfnmalg59hawlm702uuplzhszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyknlvrvx In reply to <a href='/nevent1qqsy25zd94sms03eplthr67ge4y7v9hzy8c0geen32ztlakqys0ktwq8zcaz0'>nevent1q…caz0</a><br/>_________________________<br/><br/>&gt; Are these the only two meeting some nice constraints, or are there more?<br/><br/>Yes, I believe these are the only two convex dodecahedra whose faces are congruent rhombi. That belief of mine is based on this article of Grümbaum <a href="https://faculty.washington.edu/moishe/branko/BG285%20Bilinski%20dodecahedron.pdf">https://faculty.washington.edu/moishe/branko/BG285%20Bilinski%20dodecahedron.pdf</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/806/899/705/811/992/original/318c9baf5b2a5aba.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/806/899/762/572/486/original/3787832c1b3a6c95.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/806/899/824/625/574/original/99096701e6f07c39.jpeg"> <br/> 2025-07-06T15:04:29Z https://njump.me/nevent1qqszsptevnt28nkgpa4d7hg2pz3rcke60c7qda5647mfpf5dwea54qgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykgt84ft In reply to <a href='/nevent1qqs2dnmthm8cffz45yrdntf0e0sa7rfmlhus6sp8x6mavpymx7p9zaqpquar5'>nevent1q…uar5</a><br/>_________________________<br/><br/>It stands in roughly the same relation to the normal rhombic dodecahedron as US paper does to international standard paper: it&#39;s made from rhombuses whose long diagonal is ϕ times the short diagonal, whereas the normal rhombic dodecahedron is made from rhombuses whose long diagonal is √2 times the short diagonal. 2025-07-06T08:22:55Z https://njump.me/nevent1qqs2dnmthm8cffz45yrdntf0e0sa7rfmlhus6sp8x6mavpymx7p9zaqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykg77kup In reply to <a href='/nevent1qqs8ag9wenuwcu9lhtt3nwjm5y95evcs5nk6jja97jghrjw7p3nux5qj2a2mx'>nevent1q…a2mx</a><br/>_________________________<br/><br/>It was (re)discovered in 1960 by a chap called Stanko Bilinski. <a href="https://en.wikipedia.org/wiki/Bilinski_dodecahedron">https://en.wikipedia.org/wiki/Bilinski_dodecahedron</a> 2025-07-06T08:15:54Z https://njump.me/nevent1qqs8ag9wenuwcu9lhtt3nwjm5y95evcs5nk6jja97jghrjw7p3nux5qzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykhfgh4t Did you all know that there is a SECOND rhombic dodecahedron whose faces are all congruent rhombuses, that is less symmetrical than the normal rhombic dodecahedron?<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/805/287/168/448/878/original/8072f205cfafb67a.png"> <br/> 2025-07-06T08:14:42Z https://njump.me/nevent1qqsv7vjaz5ssn20rmn4yh5eugh9r0u3lnsmvfkctg54memj97f87eegzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykhq6ksv Building a monostable tetrahedron <a href="https://arxiv.org/abs/2506.19244">https://arxiv.org/abs/2506.19244</a> 2025-06-25T20:01:46Z https://njump.me/nevent1qqsgl7tzsvdjux7l24vc062nfklrpuu30ty5xkyezy4gy55rpr7ck4szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk08qaj0 In reply to <a href='/nevent1qqsd4hnj4y0pavmrne3pqcenv7fk58wuenk2z9fdxu6ndta4nyxc5wstakp2k'>nevent1q…kp2k</a><br/>_________________________<br/><br/>Do you think most laypeople would regard “these shapes as identical” as true if one were a uniformly scaled copy of the other?<br/><br/>(If not, what do we call that? My schema would suggest ‘simila’, of course.) 2025-06-15T14:11:29Z https://njump.me/nevent1qqs2jhmx884fxhxhd3n440mg083tt6ype2a9ckctpqsma6up5c4vnlgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykl4ae2c There really should be a word for when two geometric objects are related by a direct (positive) isometry – i.e. they&#39;re actually the same size and shape, not mirror images of each other.<br/><br/>I sometimes say ‘congruent’, but technically that includes mirror images as well, so isn&#39;t what I really meant.<br/><br/>If there really isn&#39;t a word for this, can I propose ‘conguent’ – i.e. congruent without the (r)eflections?<br/><br/>This has the added benefit that it will give copy editors the heebie-jeebies. 2025-06-15T13:54:24Z https://njump.me/nevent1qqs9pd59m7kuksj6anyuk8zhg0p2rjs7zyjy9q562307yhfq2vhy9tgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk4uc33m In reply to <a href='/nevent1qqsxtgdrtm6up8sj6mx5d50afmxvp69asktj4tzlnuyadreexcahqxgclqvtv'>nevent1q…qvtv</a><br/>_________________________<br/><br/>I made a book of ten thousand times no, and it’s only 13 pages long, which is shorter than I would have guessed. I can’t share PDFs on here, so here are the first two pages. You can imagine the rest.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/687/233/881/760/090/original/f297fdb98901fb53.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/687/238/877/244/724/original/e9f1717b32e57601.jpeg"> <br/> 2025-06-15T11:53:57Z https://njump.me/nevent1qqsd5kxnz64yaeprwkdhjd2f9g63qmx6cjqh0ahtkvp264q5yrftzcszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykslhp6h Here&#39;s a puzzle of my own invention, which is probably quite hard if you don&#39;t have a physical copy and you have to do all the manipulation in your head. The puzzle is to assemble these eight pieces into a 4×4×4 cube. (Don&#39;t worry about the colours, they don&#39;t mean anything.)<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/686/924/580/850/571/original/e7333878c280a851.jpeg"> <br/> 2025-06-15T10:35:33Z https://njump.me/nevent1qqswdt36zvpe0ej36dgem36ykcajz040f87ry9fl504nucdw3rpspjgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyksdflq4 I haven’t found Claude very useful for actually working things out, yet, but it’s brilliant at visualising things you’ve worked out in some other way! <a href="https://claude.ai/public/artifacts/a53161cf-8186-41a5-b223-732dfb426f5c">https://claude.ai/public/artifacts/a53161cf-8186-41a5-b223-732dfb426f5c</a> 2025-06-11T22:01:03Z https://njump.me/nevent1qqs2qe3wucjagzf0mslz59vam699masavvhac6je77hulahz98pl3egzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk8uns42 This is a fun puzzle from Inigo Quilez at the bad place.<br/><br/>It&#39;s shorter than you&#39;re probably thinking even if you&#39;re taking account of the fact that it&#39;s shorter than you&#39;re probably thinking.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/599/134/974/700/366/original/8b12fd6bdc5e4a65.jpeg"> <br/> 2025-05-30T22:30:08Z https://njump.me/nevent1qqsqx8vmmzmxcz46ykmvcj7smcy0wfklp65mtrg7zu3f3hcdlxx4prqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk6d6exa Fun fact (via otaliptus on Twitter): the president-elect of Romania was one of the 11 students to solve the famous Vieta jumping problem at the 1988 IMO: <a href="https://en.wikipedia.org/wiki/Vieta_jumping#History">https://en.wikipedia.org/wiki/Vieta_jumping#History</a> 2025-05-19T11:22:19Z https://njump.me/nevent1qqszl0uxafux399pnjvwdk23rn32zxzn5qvskd6p403fzj74u502slgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk7yr32v In reply to <a href='/nevent1qqsxgp2q5kn6x46yln8ru7535ruhx4am6835acp2tz7dt7w29l7cl6ctz88q4'>nevent1q…88q4</a><br/>_________________________<br/><br/>I can see *what* they do, I just can&#39;t imagine *why* :-) 2025-05-10T07:46:05Z https://njump.me/nevent1qqsqnt0rffqqmw0vxh8ns2s8nzktc5f40mqknmqd4fxhng32904qa3gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyktym3u9 In reply to <a href='/nevent1qqs2y9kdqglyrmcm3sug5ksagr7tf0ucds3a76rrv6clxdqz9d77qxsylfpj8'>nevent1q…fpj8</a><br/>_________________________<br/><br/>How intriguing! I wondered if its intent would seem obvious from the code, but it doesn&#39;t seem obvious to me. Do you understand it?<br/><br/>(The only part that seems fairly easy is the part that converts lowercase ASCII letters to their uppercase counterpart.)<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/482/404/842/584/762/original/02241b545df9925d.jpeg"> <br/> 2025-05-10T07:43:41Z https://njump.me/nevent1qqsdlxyl23ckjm6erxfp4smr96qv0rexjpkkvkjy80vk8lzuzg08euqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk9s40af In reply to <a href='/nevent1qqs2z84jj3p0pkd23mkgjxk3g5hrjzpn9hrn2j2fgmj6wmzwzhq6z4stkm7rz'>nevent1q…m7rz</a><br/>_________________________<br/><br/>Yes, that fits with what I imagined it meant. I haven&#39;t thought about it seriously. I suppose another possible interpretation of the first condition would just be that the rings are pairwise linked, but knowing Conway the automorphism interpretation seems more likely. 2025-05-02T07:48:48Z https://njump.me/nevent1qqsyx9d7t5jcacd5qudhahk62dr2mkwp90lemp5e72r2gaj5zqvxp3szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk5enx7z In reply to <a href='/nevent1qqs95kumn7rg4jmx8e2f7cevkwvjdqfpf6lq0g5qfyycuyhzn77m0scq0lpfx'>nevent1q…lpfx</a><br/>_________________________<br/><br/>I think the prize was only offered for correct solutions submitted on the day itself (2016-03-14), so unfortunately you wouldn&#39;t even get pizza for it now. 2025-05-02T07:30:06Z https://njump.me/nevent1qqsvx5qn7jj65h9ydhdcwrj68e575e09dyqfjueert9ucqj4jng3qlqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykg45a6w In reply to <a href='/nevent1qqsx7982ptxrrr0xndpn8f5ng9axlpq6um3zw04yswsg2xrdfv26tfgu7m62q'>nevent1q…m62q</a><br/>_________________________<br/><br/>Here&#39;s the third, unsolved, problem:<br/><br/>My key-rings are metal circles of diameter about two inches. They are all linked together in a strange jumble, so that try as I might, I can’t tell any pair from any other pair.<br/><br/>However, I can tell some triple from other triples, even though I’ve never been able to distinguish left from right. What are the possible numbers of key-rings in this jumble? 2025-05-02T04:06:41Z https://njump.me/nevent1qqsx7982ptxrrr0xndpn8f5ng9axlpq6um3zw04yswsg2xrdfv26tfgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykdngp9n In 2016, as a publicity stunt for Pi Day, the US chain restaurant Pizza Hut announced a trio of mathematical puzzles written by John H Conway, offering prizes of Pizza Hut gift cards.<br/><br/>The first two problems were successfully solved, and prizes presumably awarded, but the third was not and seemingly remains unsolved to this day!<br/><br/><a href="https://blog.pizzahut.com/pizza-hut-partners-with-mathematician-john-h-conway-for-national-pi-day-math-contest/">https://blog.pizzahut.com/pizza-hut-partners-with-mathematician-john-h-conway-for-national-pi-day-math-contest/</a><br/><br/><a href="https://blog.pizzahut.com/national-pi-day-math-contest-problems-are-here-2/">https://blog.pizzahut.com/national-pi-day-math-contest-problems-are-here-2/</a> 2025-05-02T04:05:58Z https://njump.me/nevent1qqsyr0gtjjpdummeuxeexu4vy7g63j35z20dxy229v6qga27jete80gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykd5g6jn Happy Gauss&#39;s Birthday, everyone! I hope you&#39;re having a good one. 2025-04-30T12:04:04Z https://njump.me/nevent1qqsdssc8kx8sxhhhwmsemvh873ee6jsmsj076ey0x5ms60d5ejqq38szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykqjhl0d In reply to <a href='/nevent1qqs9uhlrgd24umwje0xleywc9uknamdmfs67fd0stsgyrdy3kfru7qcpaq93t'>nevent1q…q93t</a><br/>_________________________<br/><br/>On reflection, the confusion might be the result of a misguided analogy with adjectives such as ‘uncovered’ – since the verb ‘to cover’ has the opposite relationship with the noun ‘cover’ than ‘to shell’ with ‘shell’. 2025-03-30T13:01:26Z https://njump.me/nevent1qqs9uhlrgd24umwje0xleywc9uknamdmfs67fd0stsgyrdy3kfru7qczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk59z5c0 In reply to <a href='/nevent1qqsfmte4val0d73kq80vugvgawrcvldpmc55ae3g656ah0ty8r4sc6sugnt5y'>nevent1q…nt5y</a><br/>_________________________<br/><br/>Hot take: this is not in fact ambiguous, since the formation “un-X-ed” requires X to be a verb, and the verb “to shell” has an unambiguous meaning.<br/><br/>But it should probably be avoided anyway, since apparently it will be misunderstood by a large proportion of people. 2025-03-30T12:58:16Z https://njump.me/nevent1qqsw8duf3802wp4rp4rlxkjdcl73qxjkpeaq9v4zg0lsgwspy5a7fygzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykd8uwwr In reply to <a href='/nevent1qqsgdewxgnggs3fmgywunnez54336n6u06n46majtdtgskj7qfnplwgnx9hqq'>nevent1q…9hqq</a><br/>_________________________<br/><br/>I thought the list of still-unsolved problems at the end of the paper was interesting:<br/><br/>* Is a three-piece dissection still impossible if flipping is allowed?<br/><br/>* Are there only a finite number of rectangles that can be dissected into three pieces from a triangle? If so, how can they be enumerated?<br/><br/>* Are there any other four-piece dissections between an equilateral triangle and a square, aside from the solution proposed by Dudeney?<br/><br/>* Are there any pairs of regular n-gons and m-gons that can be dissected into three pieces, where n ≠ m?<br/><br/>* Is a three-piece dissection still impossible if we allow nonpolygonal (curved) pieces? 2025-02-15T16:34:53Z https://njump.me/nevent1qqsrjqzhmzhmf68p8v8zytncdwee9f9wfd3zd6vrkndk6pnydvrdfsczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk4q8w9p From December, but I missed it at the time: Dudeney&#39;s Dissection is Optimal <a href="https://arxiv.org/abs/2412.03865">https://arxiv.org/abs/2412.03865</a> 2025-02-15T07:12:49Z https://njump.me/nevent1qqspccwkzq5q66ffhwedgl3tuyf7c59lek65rxttxs92fa5qavxs9qszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk304z7n In reply to <a href='/nevent1qqsznks7qsdeq88v6ngdkj4m6wptewmanedr6xprh0zuca0a5jnzn9stdvfpc'>nevent1q…vfpc</a><br/>_________________________<br/><br/>I assumed he was referring to François Morrelet&#39;s red and blue wallpaper 2025-01-31T17:26:11Z https://njump.me/nevent1qqs2y6rpptv3kvumyd6mssh84muecw9y6dgg55jvlgtz5r0lj8vp57gzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyke9vh63 In reply to <a href='/nevent1qqsv70hypddu5tc0rph0pc8k5matnhvaqjf6amvw5d2dy8vyahmrq8gvp4rju'>nevent1q…4rju</a><br/>_________________________<br/><br/>it creates a very powerful effect when you&#39;re in the room! 2025-01-31T17:12:08Z https://njump.me/nevent1qqst8waajgmuzqyhud283l4me3nylkzd3ahs554u52x9l6kj56v6vrczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykyhkwnd If you&#39;re interested in algorithmic art, and within striking distance of London, I&#39;d recommend the Electric Dreams exhibition at Tate Modern<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/924/064/098/742/522/original/6464770bfe441a3c.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/924/064/278/494/129/original/57e92aaacc6c3dfd.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/924/064/704/269/390/original/74ed8ba1b92b5713.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/924/065/015/801/331/original/cd6fa4daf14a9dd4.jpeg"> <br/> 2025-01-31T17:08:20Z https://njump.me/nevent1qqs8lpappm0le3ld26ghqsl77fztlezqt2wzvmgpnwx6tfhylphp3xszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk9sdelh I&#39;ve recently discovered that there&#39;s at least one creator who posts amazingly high-quality mathematical visualisations to TikTok. Sorry Americans.<br/><video controls width="100%" class="max-h-[90vh] bg-neutral-300 dark:bg-zinc-700"><source src="https://media.mathstodon.xyz/media_attachments/files/113/853/245/635/213/620/original/03e1c45e44c37324.mp4"></video><br/> 2025-01-19T04:58:45Z https://njump.me/nevent1qqsrwmeluxktgydwz7sjwuagw6awexpsf5uh0f6jquuvcnwjvkqhhpgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyky43mhz A very nice article by <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1p5zwqctkgq05ck6cm8v2mn48q9zwssfns7ks533njxt6aac865ssnz4d3n" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>0xDE</span> (<span class="italic">npub1p5z…4d3n</span>)</a></span> in the AMS Notices, on the important concept of the treewidth of a graph. <a href="https://www.ams.org/journals/notices/202502/noti3043/noti3043.html">https://www.ams.org/journals/notices/202502/noti3043/noti3043.html</a> 2025-01-14T11:22:24Z https://njump.me/nevent1qqsdjt867yw4cu0rsp9x5spvv50tm4xxnuk9glj9flqkmpulf6zr9eszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykkjn4kw In reply to <a href='/nevent1qqsf22rzasju86zrsw6ktdcgsuuzmeky5sed034pgkdz0rdjpzg2yvsvs2d4s'>nevent1q…2d4s</a><br/>_________________________<br/><br/>Thanks! That whole discussion is interesting. 2025-01-08T11:56:37Z https://njump.me/nevent1qqspshdt9qxjdee6pg0pzyaljty3wxsavhrsd0p0dgua9vuqdgzm30szyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykl26z9w Because it&#39;s 2025, we&#39;re all thinking about the identity \[\Bigl(\sum_{i=0}^ni\Bigr)^2<br/>=<br/>\sum_{i=0}^ni^3\]<br/><br/>I&#39;m now wondering how closely this is related to the similar (but in a way simpler) identity<br/>\[<br/>\Bigl(\int_{0}^nx\,dx\Bigr)^2<br/>=<br/>\int_{0}^nx^3\,dx<br/>\]<br/><br/>Is the former a direct consequence of the latter? 2025-01-08T11:37:16Z https://njump.me/nevent1qqs272jhuer9pk97kpa5wp84k38qylnlq54lc0pnanpseeramw2dfmczyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykdxse4d I like this rant: I never found Gabriel&#39;s horn / Torricelli&#39;s trumpet to contradict my intuition, though it&#39;s a fun example. <a href="https://intellectualmathematics.com/blog/torricellis-trumpet-is-not-counterintuitive/">https://intellectualmathematics.com/blog/torricellis-trumpet-is-not-counterintuitive/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/753/072/051/438/046/original/99261d43a8eda9a2.jpeg"> <br/> 2025-01-01T12:22:36Z https://njump.me/nevent1qqsg72p3ng7qwp3zfa4k7k9kvm9azp5n5tl8vnu58mkkr6yaqclfmtgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk6fpdda There&#39;s a new preprint that claims to prove that Gerver&#39;s sofa is optimal.<br/><br/>Have any of you read it yet? Big if true!<br/><br/><a href="https://arxiv.org/abs/2411.19826">https://arxiv.org/abs/2411.19826</a> 2024-12-03T04:14:57Z https://njump.me/nevent1qqsxca669xc7huzhdmw7rh6guptv9whhtsxgze8h5lpkxzewwpnjk2czyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykm6w7s7 I enjoyed this nicely animated video on the Mandelbrot set, Julia sets, etc. The music appears to be cleverly synchronised with the animation, which is a nice touch. <a href="https://youtu.be/Ed1gsyxxwM0">https://youtu.be/Ed1gsyxxwM0</a> 2024-11-28T08:10:44Z https://njump.me/nevent1qqsdl96k35ffdn6r5dc9xxj92tctlf2jza2uvfz2avjddds36fu8wjszyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk3c7dws <a href="https://saytheprime.com/">https://saytheprime.com/</a> 2024-11-02T15:58:27Z https://njump.me/nevent1qqs2dxd3tvt57d98k49uy2c0ltttafyss75dtzg50cga823l29gz6lqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykrmzayz In reply to <a href='/nevent1qqsrjfwtv304u45t3pffevthvyupjuqt85h8rcypnsdhvav3gkmdpeqn86chx'>nevent1q…6chx</a><br/>_________________________<br/><br/>The cat&#39;s out of the bag: I can relax now. <a href="https://www.mersenne.org/">https://www.mersenne.org/</a> 2024-10-21T14:20:49Z https://njump.me/nevent1qqsrjfwtv304u45t3pffevthvyupjuqt85h8rcypnsdhvav3gkmdpeqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykm03dmp I found out the exponent of the new Mersenne prime before it’s been officially announced, and I feel as though I’m in possession of a deep, dark secret.<br/><br/>I hope I’m not giving too much away if I remark that in base 10 it has a number of digits that is a multiple of 80, which means it scrolls very neatly down a standard-width terminal. 2024-10-18T21:27:56Z https://njump.me/nevent1qqsw3y7cnsmnt4d8pgyj960q3g0ln0dwtwpvswqgr0lc5gtvwy2tsmgzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk0qyawz Our determinant paper has just been published.<br/><br/><a href="https://doi.org/10.1017/S0963548324000233">https://doi.org/10.1017/S0963548324000233</a> 2024-09-18T09:04:23Z https://njump.me/nevent1qqsrk7su6xtgxajhdtq6tkactt0avfza3hs0tfuy4j7y75vclawru6czyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykajavqd I’m hearing worrying rumours that Shapeways has gone bust and closed its doors for good, though that hasn’t been officially confirmed.<br/><br/>Bad news for those of us who like to create physical three-dimensional objects without getting our hands dirty.<br/><br/>Anyone know good alternatives (perhaps based in the UK)? 2024-07-03T10:13:08Z https://njump.me/nevent1qqs2lfztyz0ddngxhxuh2l0ypdk9ujmqzs5n0r6tjrjrqlamdy06pfqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hyk6ec4td This is an exciting moment for me! The official public unveiling of a polyhedron I found a couple of years ago. Along with lots of interesting back story etc. from <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1g3p455drsucxfesdn9ccelj4z8l4vlpj7j8j6tj97t92k6qlu59q3yjcyf" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Matt Parker</span> (<span class="italic">npub1g3p…jcyf</span>)</a></span> <a href="https://youtu.be/daVny9y72UE?si=M5ecCCQBwzWMZ60m">https://youtu.be/daVny9y72UE?si=M5ecCCQBwzWMZ60m</a> 2024-06-05T16:12:46Z https://njump.me/nevent1qqs03qn9g80fdvttx4svh2vc5p83wn2z6ermup9wxzuvh5ws4cn4xfqzyz958cf5a4nwendke6u2e04srfsm8xkcfwmwpkcewglfevw7d8hykcvq3cq I printed two images, one on paper and one on acetate. Each is individually indistinguishable from random, but when overlaid they reveal an elephant.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/109/644/051/569/659/702/original/4de5ea80080d34cb.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/109/644/051/695/638/645/original/f28e8cbe7080f626.jpeg"> <br/> <img src="https://media.mathstodon.xyz/media_attachments/files/109/644/051/817/487/956/original/ca019ea7ac0588c8.jpeg"> <br/> 2023-01-06T20:09:01Z