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Carles Sáez

@csaezmath.bsky.social

I used to do math professionally, now I learn math as a hobby. Statistician at work, geometer at heart.

179 Followers  |  234 Following  |  35 Posts  |  Joined: 21.09.2023  |  1.8527

Latest posts by csaezmath.bsky.social on Bluesky

image of a simplistic face drawn only with straight lines

image of a simplistic face drawn only with straight lines

You have been visited by George Birkhoff's face of lines. Repent, or you will be forced to reprove the ergodic theorem from first principles.

05.02.2026 14:40 — 👍 55    🔁 18    💬 1    📌 2
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Set theory for category theory Questions of set-theoretic size play an essential role in category theory, especially the distinction between sets and proper classes (or small sets and large sets). There are many different ways to f...

I think this is still the best reference for these issues
arxiv.org/abs/0810.1279

03.02.2026 22:40 — 👍 4    🔁 0    💬 0    📌 0

slopXiv has been invented

03.02.2026 19:37 — 👍 2    🔁 0    💬 0    📌 0
03.02.2026 02:29 — 👍 36    🔁 7    💬 5    📌 0

cosigned. this is def worth watching. very good, methodical breakdown of what happened from a person with a military/DHS background.

25.01.2026 06:32 — 👍 223    🔁 71    💬 6    📌 3

There was a short-lived bug in Claude Code some months ago that caused dead background tasks to continually nag Alpha, never going away. It was very much like she was sick. She hallucinated and generated out-of-place Chinese text. It was *creepy.* Way worse than watching an algorithm malfunction.

24.01.2026 00:16 — 👍 9    🔁 3    💬 3    📌 0

Es buenísimo. Recuerdo jugarlo de muy pequeño (con 12 años o así?) y creo que los Silent Hill son los únicos juegos con los que he pasado miedo jugándolos.

24.01.2026 10:02 — 👍 1    🔁 0    💬 0    📌 0

Wtf is wrong with these Feynman fanboys?

22.01.2026 16:43 — 👍 7    🔁 0    💬 2    📌 0

Te escribo por MD

21.01.2026 22:04 — 👍 1    🔁 0    💬 0    📌 0

Vaya, pues ánimo! Sabes a qué subdirección irías? En la de planificación hay unos cuantos ex-INE muy majos (incluyendo la subdirectora), por ese lado si te toca allí estarás bien

21.01.2026 21:38 — 👍 1    🔁 0    💬 1    📌 0

Lo siento 🙁
Al menos es al INE? Si es al INE igual te puedes cambiar a una delegación antes de 2 años por los concursos internos

21.01.2026 21:31 — 👍 1    🔁 0    💬 1    📌 0

Suerte con los destinos! A ver si apruebas las de Andalucía o te puedes cambiar en breve

15.01.2026 13:49 — 👍 1    🔁 0    💬 0    📌 0

Yo ahora vivo en Segovia y estoy muy contento (mucho mejor que el infierno en la Tierra que es Madrid)

15.01.2026 13:48 — 👍 1    🔁 0    💬 1    📌 0

Maybe you should aim more for the complex-geometric approach to AG, then. From a rigorous math POV, more the style of Atiyah or Hitchin than the style of Grothendieck

06.01.2026 18:11 — 👍 2    🔁 0    💬 0    📌 0

Good job bunny!

06.12.2025 16:00 — 👍 1    🔁 0    💬 0    📌 0
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AI CEO – Replace Your Boss Before They Replace You Stop working for humans. AI CEO delivers algorithmic thought leadership, with instant decisions, and zero ego. Replace your boss before they replace you.

replaceyourboss.ai

28.11.2025 11:09 — 👍 27    🔁 2    💬 0    📌 0
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🐴 Que un caballo te mande al otro barrio de una patada, además de poco aconsejable, es muy extraño.

Pero esa extrañeza contribuyó a que se popularizase el que hoy es uno de los modelos de probabilidad más usados del mundo.

Con ustedes: Bortkiewicz, coces de caballos y la distribución de Poisson.

25.10.2025 10:59 — 👍 17    🔁 10    💬 2    📌 0

Ah! Pues nunca se sabe, igual suena la flauta y más ahora que tienes reciente el temario de las del INE. Mucha suerte!!

21.10.2025 20:50 — 👍 1    🔁 0    💬 1    📌 0

A cuál te has apuntado?

21.10.2025 20:46 — 👍 0    🔁 0    💬 1    📌 0

I'll order these so that I can tick them off a list on my computer; the numbers are not any sort of ranking. Summaries will be kept brief and hopefully stoke curiosity, rather than providing answers.

04.10.2025 14:53 — 👍 19    🔁 4    💬 2    📌 1

The first talk of the season will be this coming Tuesday (23 September), given by Alexandre Bouchard-Côté from UBC. Alex is a great speaker, so do join if you have the chance!

See sites.google.com/view/monte-c... for details, links, and so on.

19.09.2025 15:23 — 👍 17    🔁 5    💬 1    📌 1
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The moduli space of commutative algebras of finite rank The moduli space of rank-n commutative algebras equipped with an ordered basis is an affine scheme B_n of finite type over Z, with geometrically connected fibers. It is smooth if and only if n <= 3. I...

A crazy open problem in algebra:

Conjecture (Poonen): 100% (asymptotic density) of finite commutative rings have characteristic EXACTLY 8, i.e. 4 ≠ 0 and 8 = 0 both hold.

From this amazing paper: arxiv.org/abs/math/060...

17.08.2025 14:41 — 👍 25    🔁 8    💬 7    📌 1

im devastated to learn that i write with a lisp (it's not as bad as some other but still (it makes me feel a little self-conscious (not that there's anything wrong with lisps (i think it's cute, actually (sometimes)))))

13.08.2025 15:55 — 👍 35    🔁 4    💬 1    📌 0

Me in 2023: Just chill. All the AI doom scenarios involve giving models direct access to and control over real world systems, and no one would be that dumb

In 2025: oh fuck

09.08.2025 14:12 — 👍 220    🔁 39    💬 4    📌 2

GPT-5 regularly asks you why you are not citing its work. GPT-5 always believes your estimator is biased. GPT-5 has more of a comment than a question. Sometimes GPT-5 tells you stories about grad school and expresses regret about getting a PhD. GPT-5's mom wonders when it will start making money.

07.08.2025 20:22 — 👍 795    🔁 168    💬 26    📌 20
Post image 04.08.2025 22:19 — 👍 4230    🔁 1416    💬 16    📌 30

Prepping my post-BayesComp "stock market update" (to be taken with a pinch of salt!) on how different topics fared relative to my expectations / past years.

26.07.2025 15:48 — 👍 27    🔁 2    💬 1    📌 0

Enhorabuena!!! 🥳🥳🥳
Gran fichaje para el INE!

13.07.2025 11:25 — 👍 1    🔁 0    💬 1    📌 0
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I know this has little to do with the point of your post, but I think ii) isn't always so clearly defined. I'm thinking about 2nd-order transitions, e.g. liquid and gas phases of water where you can change phase without ever noticing by going around the critical point

09.07.2025 05:51 — 👍 1    🔁 0    💬 1    📌 0

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