Alexander Grothendieck Revolutionized 20th-Century Mathematics

5/24/2026 at 6:27:27 AM

One of my favourite Grothendieck stories from <https://www.ams.org/notices/200410/fea-grothendieck-part2.pd...>:

> One striking characteristic of Grothendieck's mode of thinking is that it seemed to rely so little on examples. This can be seen in the legend of the so-called "Grothendieck prime". In a mathematical conversation, someone suggested to Grothendieck that they should consider a particular prime number. "You mean an actual number?" Grothendieck asked. The other person replied, yes, an actual prime number. Grothendieck suggested, "All right, take 57."

by susam

5/24/2026 at 8:48:59 AM

I had to follow your link to get it: I hadn't realized that 57 is not prime. At least I'm in good company.

by cbolton

5/24/2026 at 9:40:23 AM

It looks like a prime, but can be caught with the second-simplest test: sum of the digits is 12, which is divisible by 3. Hence it's divisible by 3.

(The simplest test being of course if the number is even and bigger than 2)

Edit: now that I think about it, probably should not have tried to impose ordering to the simplicity of tests. There's of course the divisibility by 5 test, which is even simpler.

by karmakurtisaani

5/24/2026 at 1:25:36 PM

John H Conway proved that the smallest number which looks prime, but isn’t is 91. https://youtu.be/S75VTAGKQpk?si=fCGilXECmCOy7T7R

“This is an important theorem, and a result I’m very proud of.”

by seanhunter

5/24/2026 at 5:37:44 PM

I just noticed that it's 60-3 without any divisibility tests.

Tao's 27 prime was much more embarassing but understandable as he's no a calculator.

Savants are for things like remembering the first million primes. Someone like Tao or Grothendieck can't remeber them beyond 20, but it doesn't mean they can't actuly reason about them.

by alkyon

5/24/2026 at 7:02:59 PM

What's Tao's 27 prime again?

by karmakurtisaani

5/24/2026 at 7:52:26 PM

Was mentioned in a twin thread:

"27 is a Tao prime. Terence Tao suggested 27 was a prime number on The Colbert Report in 2014. He was likely very nervous."

by alkyon

5/24/2026 at 11:41:44 AM

In fact, most 2 digit numbers not divisible by 2, 3, or 5 are prime. [1] The only one that's likely to ruin your day is 7 * 13 == 91, but that's self-defeating because after you think about it long enough 91 falls victim to [2].

[1] https://til.andrew-quinn.me/posts/most-2-digit-numbers-not-d...

[2]: https://en.wikipedia.org/wiki/Interesting_number_paradox

by hiAndrewQuinn

5/24/2026 at 1:36:25 PM

It's referred to as the Grothendieck Prime for this reason.

by analog31

5/24/2026 at 9:10:50 AM

Take 111 as an example.

by Npovview

5/24/2026 at 3:56:15 PM

27 is a Tao prime. Terence Tao suggested 27 was a prime number on The Colbert Report in 2014. He was likely very nervous.

by manfromchina1

5/24/2026 at 12:42:47 PM

For anyone interested in Grothendieck's opinions on kimchi …

https://mikepierce.github.io/grothendieck-kimchi/translation...

by mkprc

5/24/2026 at 1:24:32 PM

all mention of aekjeot (fish sauce) and saeujeot (tiny shrimp) seems to be elided here. kimchi in coastal regions (and most commercialized korean kimchi) has a strong tendency to have that in, so if you take grothendieck's recipe as is, you won't have the exported korean taste. northern kimchis have diverged materially in addition, due to north korea being fucked up. aekjeot you can just add but the procedure to add saeujeot traditionally is pretty fiddly

he mentions using whatever herbs he had in a european setting like juniper and rosemary but the canonical herb to add is korean chives and dropwort. never seen juniper or rosemary, frankly.

he does mention that the pepper is a specific variety in korea without exception. this is the korean chili, sun-dried and flaked. it's a very distinctive varietal, the taste will be very different without it

by curuinor

5/24/2026 at 11:16:06 AM

If anyone's interested in Grothendieck's writing, which is primarily in French, I threw his "Séminaires de Géométrie Algébrique" (SGA, Algebraic Geometry Seminars) and "Éléments de Géométrie Algébrique" (EGA, Elements of Algebraic Geometry) into an LLM to translate it to English. It's spotty in some sections, so I intend to do another pass, but it's better than my remedial French.

EGA: https://github.com/jcreinhold/ega (https://jcreinhold.github.io/ega/)

SGA: https://github.com/jcreinhold/sga (https://jcreinhold.github.io/sga/)

by jcreinhold

5/24/2026 at 3:12:41 PM

I maintain a website of scans of things Grothendieck wrote, pictures, etc. https://wstein.org/sga/

by williamstein

5/24/2026 at 5:05:25 AM

Happy to see that it's got the obligatory monk/wizard photo.

For more life and times stuff I also suggest Labatut's Cease to Understand the World book and https://theanarchistlibrary.org/library/konstantinos-foutzop...

by ian_j_butler

5/24/2026 at 5:57:42 AM

That book is fiction with a factual veneer. I liked it a lot until I started realizing that many of the details were made up. Then I couldn't read any more. It was like when TwoSetViolin described what it was like for them to watch movies with musician characters played, unrealistically, by non-musician actors. You'd be watching the perfectly fine movie until you noticed that the bananas were blue instead of yellow, with nobody mentioning it. After that the movie made no sense any more.

I hated the movie Oppenheimer for the same reason.

by throwaway81523

5/24/2026 at 6:25:46 AM

> That book is fiction with a factual veneer.

Definitely, but do check the link.. I dug it up originally by trying to track down detail about the nonfiction background that the book is pulling from. Seems like the best short source, but I'd love to hear recs for a good biography. The autobiography that Groth is careful to say is not an autobiography is on my shelf and also in pdf form. Haven't read it yet, but I'm not sure it's the type of thing that's going to cover the descent into madness properly.

https://web.ma.utexas.edu/users/slaoui/notes/recoltes_et_sem...

by ian_j_butler

5/24/2026 at 6:56:21 AM

There is an incredible (alas unfinished) multipart Grothendieck biography by the German mathematician Winfried Scharlau: Wer ist Alexander Grothendieck? Anarchie, Mathematik, Spiritualität, Einsamkeit. I think an English translation exists, at least for the first and in my opinion most interesting volume: Anarchy. It mostly deals with Grothendieck’s childhood and his parents, who lived unbelievably fascinating lives as anarchists in pre-war Berlin.

by schrototo

5/24/2026 at 7:32:02 AM

The other article looks interesting, though it too has "blue banana" errors. Laurent Schwartz's autobiography "A Mathematician Grapples With His Century" has a more believable account of Schwartz and Dieudonné's work with Grothendieck. The Grothendieck Circle website (https://webusers.imj-prg.fr/~leila.schneps/mitanni/grothendi... since they haven't done a good job renewing domains) has a lot of Grothendieck's own writings (mostly in French) and Wilfried Scharlau's biography (in German). I tried to read those some years back but my language skills weren't up to it. Machine translation is much better now than it was then, so I might try the lazy approach.

by throwaway81523

5/24/2026 at 7:43:50 AM

I read and enjoyed that book out of a general interest in the history of ideas, but admit I am not able to judge the underlying mathematics. Is the "fiction" part only related to descriptions of his mathematical contributions, or are there problems with the biographical information as well?

by thedailymail

5/24/2026 at 10:47:49 AM

Personally, just from the implausible level of first-person detail throughout I thought it's immediately clear the book is exceptionally well-researched but still technically qualifies as historical-fiction. We don't necessarily know what these people thought/ate/did minute by minute on the important days at that level.

But I think the biggest "sin" in terms of mixing fact/fiction was mostly implied and not actually stated. What's implied is that Groth saw inside mathematics some kind of terrible truth that motivated him to stop working and withdraw from the world. I don't think it's stated explicitly, but due to proximity with other topics in the book, reader is invited to conclude that there was a discovery of some kind inevitable doom, possibly a super weapon, etc.

We don't know that, but in a lot of ways it might be more surprising if he never thought along those lines. My understanding is that the other limited sources really do say he was talking to God in dreams, preoccupied with apocalyptic visions, became more interested in physics, politics, religion, the problem of evil, hostile entities ambiguously demonic, etc

by ian_j_butler

5/24/2026 at 6:44:22 AM

Interestingly, von Neumann's daughter was kind of shocked by the research the author did for the book The MANIAC; as a kid she carried graph paper in her pocket and Labatut had somehow found this out in his research and put it into the book, really blew her away I guess.

by helterskelter

5/24/2026 at 2:48:23 PM

Very interested in reading your list of blue bananas in Oppenheimer.

by srean

5/24/2026 at 12:11:42 PM

Field medals are still handed out to people who deign to look upon his prophetic ramblings. I'm half-convinced the religious stuff probably unveils the geometric structure of the universe.

by stardustrosalia

5/24/2026 at 11:02:16 AM

[dead]

by stotemoat

5/24/2026 at 1:17:06 PM

[flagged]

by SeattleAntifa