Alexander Grothendieck Revolutionized 20th-Century Mathematics

https://www.quantamagazine.org/how-alexander-grothendieck-revolutionized-20th-century-mathematics-20260520/

Comments

susamMay 24, 2026, 6:27 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."

assemblymanMay 24, 2026, 11:25 PM
As a curiosity, the contrast between Grothendieck and Ramanujan is very striking. One famous story about Ramanujan from Wikipedia (https://en.wikipedia.org/wiki/1729_(number)):

"Hardy stated that the number 1729 from a taxicab he rode was a "dull" number and "hopefully it is not unfavourable omen", but Ramanujan remarked that "it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways"."

They, of course, were very different personalities, doing very different mathematics with very different impacts on the field. I always found it interesting that Ramanujan seemed to be very comfortable with numbers, their properties, patterns (continued fractions) and Grothendieck was very comfortable with structures and their rhythms without paying attention to concrete examples.

cboltonMay 24, 2026, 8:48 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.
karmakurtisaaniMay 24, 2026, 9:40 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.

seanhunterMay 24, 2026, 1:25 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.”

hiAndrewQuinnMay 24, 2026, 11:41 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

alkyonMay 24, 2026, 5:37 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.

karmakurtisaaniMay 24, 2026, 7:02 PM
What's Tao's 27 prime again?
alkyonMay 24, 2026, 7:52 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."

tensegristMay 24, 2026, 8:06 PM
there was some interview where he illustrated the idea of a twin prime pair using 27 and 29
analog31May 24, 2026, 1:36 PM
It's referred to as the Grothendieck Prime for this reason.
NpovviewMay 24, 2026, 9:10 AM
Take 111 as an example.
manfromchina1May 24, 2026, 3:56 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.
mkprcMay 24, 2026, 12:42 PM
For anyone interested in Grothendieck's opinions on kimchi …

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

curuinorMay 24, 2026, 1:24 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

agnosticmantisMay 25, 2026, 3:24 AM
Likely because Grothendieck was a vegetarian, at least later in his life.
williamsteinMay 24, 2026, 3:12 PM
I maintain a website of scans of things Grothendieck wrote, pictures, etc. https://wstein.org/sga/
jcreinholdMay 24, 2026, 11:16 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/)

jojomoddingMay 24, 2026, 10:02 PM
Interestingly, the way in which Grothendieck conceived of equality is nowadays being questioned, especially due to the rise of formalized mathematics and Lean. More concretely, there is this fun paper by Kevin Buzzard which deconstructs it: https://arxiv.org/abs/2405.10387

Money quote:

> In this paper I argue that the first assertion above is false, the second is dan- gerous, and the third is meaningless.

ian_j_butlerMay 24, 2026, 5:05 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...

throwaway81523May 24, 2026, 5:57 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.

ian_j_butlerMay 24, 2026, 6:25 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...

schrototoMay 24, 2026, 6:56 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.
throwaway81523May 24, 2026, 7:32 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.
thedailymailMay 24, 2026, 7:43 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?
ian_j_butlerMay 24, 2026, 10:47 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

helterskelterMay 24, 2026, 6:44 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.
sreanMay 24, 2026, 2:48 PM
Very interested in reading your list of blue bananas in Oppenheimer.
assemblymanMay 24, 2026, 11:17 PM
Peter Woit (https://www.math.columbia.edu/~woit/wordpress/) has occasionally posted about Grothendieck's life and work. E.g.

Articles on his life: https://www.math.columbia.edu/~woit/wordpress/?p=7335

Two Titans (Grothendieck and Witten) - https://www.math.columbia.edu/~woit/wordpress/?p=12868

AMS Math articles on Grothendieck - https://www.math.columbia.edu/~woit/wordpress/?p=78

practalMay 25, 2026, 9:03 AM
Super. I always wanted to learn about sheaves and schemes and the like, and this gives a simple introduction that really motivates digging deeper into the details.

It is also immediately clear why this plays a role in semantics for logics: although a ring is not that important in logic (I would think), the idea to study a theory through its syntactical consequences turned into semantics is very natural, and exactly what I do for abstraction logic as well, in particular via "valuation spaces". And it has the same property, once you set up everything the right way, things like completeness just automatically flow out of it.

stotemoatMay 24, 2026, 11:02 AM
Not one mention of why he chose to leave those top universities.... It was because of their connection to the military industrial complex.
SeattleAntifaMay 24, 2026, 1:17 PM
[flagged]
stardustrosaliaMay 24, 2026, 12:11 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.