⏚ Antoine Chambert-Loir

https://mathstodon.xyz/@antoinechambertloir

- Apprentice mathematician (Professor at Université Paris Cité),
interested in algebraic geometry, number theory and (more recently) proof formalization
- Apprentice musician (drums, tabla, cajon; previously Diderock; a rarely meeting jazz trio/quartet).
- Apprentice progressist.

In love with math, jazz, indian music and poetry. ⏚

Web: https://webusers.imj-prg.fr/~antoine.chambert-loir/index.xhtml
Blog: https://freedommathdance.blogspot.com
Orcid: https://orcid.org/0000-0001-8485-7711
BookWyrm: achambert-loir@bw.heraut.eu

Public Key

npub1j7kvjvr8hkvwzvs889v2ycwpvh0n7qns5ha84xzh2r36zrakk4wsc6a4dl

NIP-05 Address

antoinechambertloir_at_mathstodon.xyz@momostr.pink

Profile Code

nprofile1qqsf0txfxpnmmx8pxgrnjk9zv8qkthelqfc2t7n6npt4pcapp7mt2hgpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsyz9600

Publishing to

relay.damus.io

nos.lol

Author Public Key

npub1j7kvjvr8hkvwzvs889v2ycwpvh0n7qns5ha84xzh2r36zrakk4wsc6a4dl

Show more details

Last Notes

2026-06-13 14:08:19 UTC

- reply

je ne pourrai pas y être, je surveille un examen à la même heure...

2026-06-13 09:53:09 UTC

18 juin - Journée IA et apprentissage des mathématiques, organisée par la Société mathématique de France.
À l'occasion de son Assemblée Générale du 18 juin (à Paris), la SMF, en partenariat avec l'UFR de mathématiques de Sorbonne Université, organise une matinée table-ronde / débat autour de l'intrusion de l'IA dans les enseignements et nos cursus de maths au niveau universitaire. Il sera question aussi de faire le point sur l'usage des assistants de preuves (de type Lean) dans nos enseignements.
https://smf.emath.fr/evenements-smf/journee-ia-apprentissage-mathematiques

2026-05-09 11:26:27 UTC

- reply

I know that this is not the trend, but I have never been willing to propose PhD topics that would be at the level of the average thing somebody can do with the tools that are on the market, because this already requires a substantial time of the PhD project and in was already clear — at least in my field — that this would wouldn't be sufficient to get hired. So I manage to suggest questions that could be damn hard, but for which several approaches are likely to tell something at least mildly interesting, and let's see what comes out of it.

2026-05-05 13:44:10 UTC

- reply

👏 L'avertissement dit la chose suivante :
Il y a 1 + n fichiers de configuration de polices, l'un pour le système, et les autres pour les utilisateur·ices qui l'ont réclamé via `updamap-user`. Si d'aventure tu ajoutais une police pour tout le monde via `updmap-sys…`, il faudrait que tu fasses le même ajout pour toi-même via `updmap-user…` parce que ton fichier ne serait pas mis à jour par la commande `updmap-sys`.

2026-05-05 12:54:53 UTC

- reply

On dirait qu'il manque l'étape `updmap`, la moins drôle.
Donc, en ligne de commande, entrer :
updmap-user --enable Map=emerald.map
@npub1hnl…k2tt @npub12u6…q3pu

2026-05-05 10:38:38 UTC

- reply

(Je suis tombé dans TeX quand j'étais petit. Ce README est assez pourri.)
Pour savoir où créer le répertoire texmf, tu peux entrer (en ligne de commande) :
kpsewhich -var-value=TEXMFHOME
et créer le répertoire en question s'il n'existe pas déjà. (Probablement $HOME/texmf)

2026-05-05 10:20:12 UTC

- reply

L'installation est un peu casse-pieds.
Sur https://ctan.org/pkg/emerald tu peux télécharger un .zip, là, il faut le décompresser et — malheureusement — faire ce qui est indiqué dans le fichier README (qu'il faut lire, c'est pas comme dans Alice au pays des merveilles).
En particulier, les répertoires emerald/fonts et emerald/tex doivent être copiés dans le répertoire TeX soit standard, soit local ($HOME/texmf), et ensuite il faut lancer la commande `mktexlsr` pour en informer le compilateur TeX. (Je voudrais bien te donner la ligne de commande pour faire ça sans effort, mais je ne le puis,
l'idée c'est que emerald/tex/latex/emerald/* est copié dans texmf/tex/latex/emerald, et c'est encore plus pénible pour emerald/fonts.) Tu peux faire de même avec emerald/doc
Il y a enfin le répertoire emerald/other qui contient les polices au format TrueType et je ne sais pas comment elles sont gérées sur Debian.

2026-05-02 17:49:53 UTC

- reply

I'm no economist but my answer to those questions is twofold:
* What sense does it make to compare two quantities that are not meant to be compared? Why 100% as a reference? Why not 140% ? What if other productions of values are added to GDP?
* Do you have an idea of the private debt ratio to GDP?

2026-04-26 16:45:16 UTC

- reply

there's a slight (probably more philosophical than mathematical, at least now) difference between sets and groups, that the former were invented (as a formal theory) to furnish foundations for mathematics, at a time when it was inconceivable that not everything could be proved. “Wir wollen wissen, wir werden wissen!” In netherlands, mathematics is Wiskunde, the science of knowledge.

2026-04-20 15:53:14 UTC

- reply

la 14?

2026-03-01 17:27:54 UTC

- reply

so what discourse would you recommend?

2026-02-21 19:12:55 UTC

- reply

As said in the nlab page given above, continuous logic is a logic where “truth values” take values in the unit interval (or a bounded interval, or even R) . This doesn't mean at all that 1 would be absolutely true and 0 absolutely false, and all other values somewhere inbetween. In model theory, what truth values allow to do is building predicates, ie, loci where given properties hold. The classical quantifiers are replaced by supremum and infimum (or variants of). In classical logic, type spaces are totally discontinuous; continuous logic gives type spaces which have a richer topological structure and is pretty much adapted to a model theoretic approach to topological group actions, real-valued fields, and even some aspects of diophantine geometry. The main subtlety in the definitions comes from the (achieved) goal of having a compactness theorem.

2026-02-01 23:08:28 UTC

- reply

I had liked it, but that was some 30 years ago.

2026-02-01 22:19:43 UTC

- reply

I guess you have read David Lodge's book with that title!

2026-01-26 10:37:24 UTC

#ICM2026
The Société mathématique de France won't attend the 2026 ICM.
Their message mentions visas, personal safety, martial law, as well as anti-science behaviour and academic freedom.
https://smf.emath.fr/actualites-smf/icm-2026-motion-du-ca

2025-10-25 15:13:57 UTC

- reply

What you wrote is better than what she said, and lacks the contempt: if you're versed in that math, you recognize the stuff, if you don't, maybe you get an idea, and if you don't, the maybe you leave happy with the impression that somebody tried to explain something to you.
@npub1vqh…d49x

2025-10-04 16:19:15 UTC

Philosophy and mathematics: one upcoming conference and one upcoming seminar:
Lead by @npub1tuz…3hxk , Philosophie de la pratique mathématique, at Collège de France, will run every Monday, 14:00-15:00 from Oct 13 to Nov. 17.
https://www.college-de-france.fr/fr/agenda/seminaire/la-philosophie-de-la-pratique-des-mathematiques-10
and Oct 15-17, the joint 2nd Conference of the European Society for the Philosophy of Mathematics & Seventeenth French Philosophy of Mathematics Workshop will take place in Université Paris Cité and Université Panthéon Sorbonne.
https://philmath.eu/2025conference/
#mathematics #philosophy

2025-08-12 13:44:08 UTC

- reply

PhD level ain't what it used to be.

2025-08-09 17:01:01 UTC

- reply

it's actually easier than one might think since the complement of the circle has two connected components. So provided you know your blue curve is connected, you just need to know it doesn't touch the circle and contains one point within the disc.

2025-08-02 18:57:31 UTC

- reply

Fran Lebowitz, *The FL reader*
Michel Faber, *Listen*

2025-07-26 15:32:39 UTC

- reply

All apologies
https://www.youtube.com/watch?v=SEVu1tcUGnc

2025-07-25 03:45:07 UTC

- reply

I'm shamefully ignorant of those things, but what is is isometry group of S_8, as a Riemannian manifold? Or maybe you're ready to relax the kind of diffeomorphisms that act on it?

2025-07-14 13:36:10 UTC

#mastobada
Billie Holiday and Lester Young — I can't get started
I've been around the world in a plane
Settled revolutions in Spain
The North Pole I have charted
But can't get started with you
And at the golf course I'm under par
Metro-Goldwyn wants me to star
I've got a house and a show place
But can't get no place with you
You're so supreme
The lyrics I write of you
Dream, dream, day and night of you
Scheme just for the sight of you
Baby but what good does it do?
https://youtu.be/ZGAvnOSbJ_M

2025-06-01 08:18:25 UTC

- reply

L'hortensia toujours
taillé trop tard, négligé,
fleurit sans rancune.

2025-04-23 21:36:00 UTC

- reply

This book brings many details, anecdotes, on a rich topic, and that gives it some appeal. However, I am extremely doubtful of the mere project to summarize 3000 years of mathematics in one book, the more if it means conflating so many diverse mathematical traditions into one word (analysis). I skimmed through the Leibniz part, and I don't see a clear discussion of what infinitesimals meant to him (a useful fiction, did he wrote), but my reading may have been too hazy. As usual, the question with history is whether we want it to validate our own practices, to color them with the gilded dust of ages, or whether we are truly interested in what people did, why and how they did it.

2025-04-08 17:53:50 UTC

- reply

OK, so one takes the part where the probability density is above some threshold, and that is the shape?

2025-04-08 17:34:05 UTC

- reply

My question is half a joke, half serious.
I have been taught that there are such a thing as protons with electrons that turn around them as the Earth turns around the sun, and then that none of this exists, that everything is a wave function, and then that everything is rather a representation of SU(2). So I don't really understand anymore what physics is talking about.

2025-04-08 17:05:27 UTC

- reply

What is the shape of a wave function?

2025-01-31 20:49:11 UTC

- reply

Onyx Boox Note 2

2025-01-30 05:34:10 UTC

- reply

it will certainly be videotaped and put on yt, and maybe streamed live. you can send an email to the first of the two organizers on that page and ask for more information.
https://philmathulm.hypotheses.org/a-propos

2024-12-17 22:00:47 UTC

- reply

not quite. most mathematicians pretend they work with ZFC but can't state the axioms. they (we) just work with a naive notion of set and the habit not to write something blatantly inconsistent.
of course, every large formalization effort brings some technical debt.
in the 80s, Pierre Cartier explained in several interviews why Bourbaki didn't make the move to categories some 20 years before while they (Cartan, Eilenberg) had basically if not invented them, then making them prominent: that would have meant rewriting 2000 pages and they felt they had better write down their ideas about Lie groups and Lie algebras.

2024-12-13 15:46:38 UTC

- reply

Some philologists I know jumped off their chair at the view of this table. I just can't be correct. They pointed out to Bernard Vitrac's magnum opus and in particular to this website where all known editions of Euclid Elements are shown, with their relations.
https://thamous.univ-rennes1.fr/php/graph_open.php?idGraph=133&projet=grecs

2024-12-08 22:32:09 UTC

- reply

a few years ago, a tv movie needed a list of victims for a crash or something like that, and they took the list of participants to a 2010 math conference in Paris...

2024-12-03 22:18:39 UTC

- reply

Wow, that's rude. I don't feel that having such an implicit use (or abuse) of notation is good for science. And it's definitely not good for pedagogy.
@npub14a5…9fse

2024-12-01 10:14:35 UTC

- reply

is it taken at dawn or at sunset ?

2024-11-28 07:22:06 UTC

- reply

Now, some French mathematicians of my field have a deep tendency to pedantism, like using « icelle » ou « icelui »

2024-11-28 07:16:17 UTC

- reply

in French, antepenultimate would be even more pedantic than penultimate

2024-11-26 06:30:37 UTC

- reply

i'd be delighted to read it then...

2024-11-21 18:55:44 UTC

- reply

He looks a bit angry. Agreely, that's not so practical.

2024-11-19 21:41:12 UTC

- reply

no, not literally.
But it is true that discussions about the way people write mathematics often use hygienic metaphors — at least in French.

2024-11-19 21:29:54 UTC

Quand j'ai publié mon livre *Algèbre corporelle*, des collègues se sont demandés si c'était un truc à faire matin et soir, et l'éditrice m'a regardé carrément mal, mais maintenant je vois que les ami·es parlent d'hygiène mathématique à propos d'autres ami·es.
http://www.item.ens.fr/journee-commune-avec-lanr-mathy/

2024-11-11 08:54:14 UTC

- reply

don't count on their incompetence to save us. this is what some democrats had expected in 1933 German.

2024-09-29 17:30:45 UTC

- reply

I feel there are two issues here.
- F1 is a sport from the previous century whose existence, given the climate crisis, is an insult to all people worrying about the fate of mankind.
- In all sports, the men and women who do the job get slaps on the hand by the sport federations, themselves full of corrupted guys, and this also is enough.

2024-09-29 17:24:20 UTC

- reply

F1 is not the field with one element?

2024-09-27 15:45:36 UTC

- reply

Je n'en ai aucune idéee !
@npub1gxj…00vd

2024-09-27 05:49:46 UTC

- reply

il m'arrive souvent d'utiliser « tu » dans un sens générique, notamment dans une tournure conditionnelle « si tu crois que..., alors il est naturel de... »

2024-09-11 20:15:54 UTC

Marine Le Pen condamnée en appel pour diffamation envers La Cimade @npub1vu4…atfc
Toute personne éprise de liberté et de justice ne pourra que s'en féliciter. Et manifester sa gratitude pour l'action de cette association, fondées par des chrétiens protestants il y a près de 100 ans, dont l'action pendant la seconde guerre mondiale a permis de sauver de nombreux Juifs, et qui œuvre chaque jour en faveur des personnes opprimées, exploitées, réfugiées, migrantes…
https://www.lemonde.fr/societe/article/2024/09/11/marine-le-pen-condamnee-en-appel-a-500-euros-d-amende-pour-diffamation-envers-la-cimade_6313248_3224.html

2024-09-05 08:20:18 UTC

- reply

des détails ?

2024-09-03 05:59:13 UTC

- reply

this is 50 years...

2024-08-17 17:03:13 UTC

I just learnt the death of Pierre Cartier, last night.
Born in 1932, he left his name to at several concepts in algebraic geometry :
Cartier divisors (those which are locally definable by a regular equation), and Cartier duality for finite group schemes, Cartier operator for differentials in characteristic p. During his long mathematical career, he showed interest in incredibly many topics, as shown by his very long list of talks at the Bourbaki seminar.
He had suffered a stroke a few years ago from which let him much weaker.
Personnally, I will remember a very lively colleague, always eager to talk about mathematics, but also ready to share anecdotes of his personal life, in particular regarding WW2 (he was a teenager, and lived in Alsace) or the Algérie decolonization war (where he had been sent as a young soldier), or about Bourbaki with whom he had a long lasting collaboration.

2024-08-17 10:32:46 UTC

- reply

are you also present on alternative platoforms such as F-Droid?

2024-08-07 09:45:50 UTC

- reply

at some moment of his life, Kafka did the same!

2024-08-05 11:29:13 UTC

- reply

https://media.mathstodon.xyz/media_attachments/files/112/909/176/494/246/998/original/59eee4861095b452.png