Jordan Ellenberg
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jsellenberg.bsky.social
Jordan Ellenberg
@jsellenberg.bsky.social
3.1K followers 160 following 410 posts
Mathematician, writer, Orioles fan, Wisconsinite, cargo shorts dad
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jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/18/d...
Dick Gross
Dick Gross died last month. Much has already been written, and during his lifetime too, about his immense contributions to modern number theory. So I won’t try to cover that here — don&…
quomodocumque.wordpress.com
January 20, 2026 at 12:48 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/19/i...
It’s a good old-fashioned Wisconsin booger-freezer out there!
One of my favorite weather sayings. And I ran into a neighbor on my way home from the errand I was running so I got to say it in person, always a treat. 3 degrees Fahrenheit, sunny and windy in Mad…
quomodocumque.wordpress.com
January 19, 2026 at 10:43 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/17/i...
If one is not to make a mess of life
“One must be fond of people and trust them if one is not to make a mess of life, and it is therefore essential that they should not let one down.” From E.M. Forster, “What I Belie…
quomodocumque.wordpress.com
January 18, 2026 at 3:13 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/12/b...
Bruhat intervals that are large hypercubes
New paper up on the arXiv! With Nicolas Libedinsky, David Plaza, José Simental, Geordie Williamson, and (unofficially) Adam Zsolt Wagner. A bunch of algebraic combinatorists! And this is a combinat…
quomodocumque.wordpress.com
January 12, 2026 at 10:03 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/05/d...
Dyadiku
I made a game. It’s like Sudoku but dyadic. It’s called Dyadiku. Try it! I’m very interested to see whether people find it playable and fun — in particular, does it admit a …
quomodocumque.wordpress.com
January 7, 2026 at 12:08 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2026/01/05/r...
Reaching the masses (not a Marxist post)
Six popular math authors, including me, did a round-table interview for the Notices of the American Mathematical Society about talking about math to the non-academic public, or, as the Notices call…
quomodocumque.wordpress.com
January 5, 2026 at 9:17 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/12/23/s...
Self-portrait with about one quarter of Richard Serra’s sculpture Equal
Visit the post for more.
quomodocumque.wordpress.com
December 24, 2025 at 4:56 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/12/19/t...
The American people have just one fixed idea
“The American people have just one fixed idea and, since that dominant thought is money, it follows that their spirit has a certain uniform and unpleasant dryness… prodigality is an unf…
quomodocumque.wordpress.com
December 20, 2025 at 2:23 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/12/12/h...
How I know zombies aren’t real
This piece of marketing doggerel from McDonald’s, concerning their Xmas-special Grinch meal, is the most foully defiling attempt to imitate Dr. Seuss’s verse I’ve ever encountered…
quomodocumque.wordpress.com
December 13, 2025 at 8:19 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/12/03/a...
Another example: sets of arcs and loops with bounded intersection
Yet another example of the kind of problem that falls under the sphere packing / cap set / Turan umbrella I blogged about last week. Let G be SL_2(Z) and H be upper triangular matrices. Then G/H is…
quomodocumque.wordpress.com
December 5, 2025 at 12:58 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/30/r...
Random Americans, ethnic stereotypes, and large language models
I have been reading about the tendency of poll respondents to overestimate the size of small population subgroups (e.g. if you ask Americans what proportion of Americans are Jews, they’ll say…
quomodocumque.wordpress.com
November 30, 2025 at 11:56 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/27/n...
“Not Vegan”
I saw a guy today wearing a hoodie that said “Not Vegan.” I’m not vegan either, not even close, but come on. This is like wearing a “Yankees Suck” shirt. I hate the Ya…
quomodocumque.wordpress.com
November 28, 2025 at 4:07 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/27/m...
Mathgiving
Happy Thanksgiving to all my American readers, and hey, everyone else too — gratitude is global. In the US, this is the start of the season where people customarily think about their charitab…
quomodocumque.wordpress.com
November 28, 2025 at 12:02 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/24/s...
Sphere packing, cap set, and the Turán problem are all the same thing
OK, they are not really the same thing. But I got you reading, right? Here’s the sense in which they’re all the same thing. Let G be a group and H < G a subgroup. Let m > 1 be an …
quomodocumque.wordpress.com
November 25, 2025 at 5:57 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/08/l...
Let us now praise United Airlines
I did manage to get home last night from Providence, despite widespread cancellations and delays caused by the government shutdown de-staffing air traffic control. United was speedy, flexible, and …
quomodocumque.wordpress.com
November 8, 2025 at 10:16 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/11/07/i...
I reviewed a book about the math foundations crisis for the New York Times
I thought the book had some interesting virtues but was also quite badly overwritten, and very confusing in its treatment of the mathematics. Here’s my review. For length reasons I wasn’…
quomodocumque.wordpress.com
November 8, 2025 at 8:17 PM
jsellenberg.bsky.social
I'm moderating an online discussion for the National Academies today, 3pm eastern, on math, risk management, and natural disasters!

www.nationalacademies.org/event/45862_...
Risk Modeling and Management for Natural Disasters Innovation by the Numbers | National Academies
Learn more from the National Academies of Sciences, Engineering, and Medicine
www.nationalacademies.org
October 14, 2025 at 2:47 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/10/08/m...
MacArthur Fellows: Wisconsin and Williams
The 2025 MacArthur Fellows have been announced, and I’m very pleased that two of the 22 awardees are my UW-Madision colleagues: congratulations to Ángel F. Adames Corraliza from atmospheric a…
quomodocumque.wordpress.com
October 10, 2025 at 12:00 AM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/09/30/c...
Claudia Prieto, “Tus Ojos”
Claudia Prieto is a Venezuelan singer-songwriter about whom I know next to nothing except that she recorded this gorgeous song, “Tus Ojos,” in 2018. By the way, I found out about this s…
quomodocumque.wordpress.com
October 5, 2025 at 2:33 PM
jsellenberg.bsky.social
quomodocumque.wordpress.com/2025/10/03/t...
Taylor Swift and Stephanie Burt, or: Life of a Harvard English Professor
It’s Taylor Swift album day! We listened to it last night at 11pm central when it went live. Snap reaction from AB, for whom 1989 is apex Swift and the last two albums have been too moody and…
quomodocumque.wordpress.com
October 4, 2025 at 1:35 AM
jsellenberg.bsky.social
I gave a talk about machine learning and math
I, too, spoke at the CMSA Big Data conference where this cool math bio talk took place. If you’ve seen me give a talk about math and machine learning lately, you’ve seen some of the sli…
quomodocumque.wordpress.com
October 4, 2025 at 1:23 AM
jsellenberg.bsky.social
Global epistasis emerges from a generic model of a complex trait (or: random walks on a hypercube with reweighting)
I still don’t really know what global epistasis is, but I really enjoyed Gautam Reddy’s talk about this paper at the CMSA Big Data conference two weeks ago. I’ll describe it, in c…
quomodocumque.wordpress.com
October 3, 2025 at 1:17 AM
jsellenberg.bsky.social
Mura Yakerson interviewed me
And we talked about math, writing, standup comedy, the art of interviewing (meta!) Mura’s whole channel is great. Bisi Agboola! Helene Esnault! Steve Strogatz! Mura’s mom! Check it out.
quomodocumque.wordpress.com
September 30, 2025 at 11:08 PM
jsellenberg.bsky.social
Klartag improves the sphere-packing constant
Hey! It escaped my notice until this week that Boaz Klartag has recently shown the existence of lattice sphere packings in dimension d of density at least c d^2 2^-d. This lower bound was stuck at …
quomodocumque.wordpress.com
September 30, 2025 at 12:52 AM
jsellenberg.bsky.social
To The Best of our Knowledge is finished
The longtime Wisconsin Public Radio show To The Best of Our Knowledge airs its last episode this weekend. You can listen to the stream at that link or you can listen to it over the airwaves tomorro…
quomodocumque.wordpress.com
September 28, 2025 at 8:21 PM