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Aaron Anderson

@awainverse.bsky.social

Model theory postdoc at UPenn

128 Followers  |  413 Following  |  45 Posts  |  Joined: 10.12.2023  |  2.3638

Latest posts by awainverse.bsky.social on Bluesky

Boolean prime ideal theorem - Wikipedia

Logic has prime ideals too en.wikipedia.org/wiki/Boolean...

18.10.2025 01:46 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0
Divisible group - Wikipedia

If you add the divisibility axioms, they become Q-vector spaces too.

(You also need torsion-free to make it unique.)

en.wikipedia.org/wiki/Divisib...

11.10.2025 00:16 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Not to mention that Vienna's the hub for the NightJets, so you can get there from all over by night train (but book early).

07.10.2025 11:58 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

The architecture in Budapest is exceptional.

The place I've been to most in that region is Vienna, which absolutely hits the "urbanist-oriented" definition - lovely by walking, biking, or tram.

07.10.2025 11:56 β€” πŸ‘ 3    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0
Map of the Universe Map of dividing lines in classification theory

One of the definitions is about not being able to put a "definable" linear order on an infinite set, but there's a nice chart with more examples here:
forkinganddividing.com#_00_2

04.10.2025 17:29 β€” πŸ‘ 1    πŸ” 1    πŸ’¬ 1    πŸ“Œ 0
Stable theory - Wikipedia

Sounds like you prefer your theories stable.

en.wikipedia.org/wiki/Stable_...

04.10.2025 17:11 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Yeah I think this is less our invention and as per usual, more us drowning out the sound of older stories (The Smith and the Devil, Stingy Jack) with a bit less subtlety and electric amplification.

02.10.2025 12:08 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

TRENTON MAKES THE WORLD TAKES

26.09.2025 15:51 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

I thought the instructions said @donoteat.bsky.social

13.09.2025 14:03 β€” πŸ‘ 0    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

In this analogy, compact metric spaces act basically like finite sets. If you look at isomorphism classes of finite sets, that's just β„•, which is a countable set. So it makes sense that you'd have a metric space of all compact (think finite) metric spaces, and it'll be separable (think countable).

05.09.2025 11:24 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

Makes sense. In continuous logic, we focus a lot on metric density: the smallest cardinality of a dense set in a given metric space. It ends up being a better notion of "cardinality" of a metric space.

05.09.2025 11:21 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

IMO it's too sweet, but the grapefruit flavor is perfect.

28.08.2025 17:15 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

The point in the contexts I'm talking about is to make the complex numbers "more real", in order to use the linear ordering on the reals to build inequalities, which can express things that systems of equations over an algebraically closed field cannot.

25.08.2025 17:53 β€” πŸ‘ 3    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0
SzemerΓ©di–Trotter theorem - Wikipedia

(The starting point to get a flavor for this kind of problem is the SzemerΓ©di-Trotter theorem) en.wikipedia.org/wiki/Szemer%...

25.08.2025 17:28 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

Unless you want to know something combinatorial, about, say, incidences, in which case you often have to embed C in R^2!

25.08.2025 17:27 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 3    πŸ“Œ 0

Do you mind sharing the flyer file to print more?

19.08.2025 00:51 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0
Preview
Amtrak’s Keystone line, connecting NYC, Philly, and Harrisburg, may get axed under SEPTA cuts U.S. Rep. Brendan Boyle said Amtrak's Keystone Service line is at risk because the railroad could lose $71.1 million in annual payments from SEPTA.

www.inquirer.com/politics/sep...

18.08.2025 21:01 β€” πŸ‘ 0    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Or downgrade "Starship" back to "Airplane", while upgrading the music.

13.08.2025 12:07 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

My data set is small and anecdotal, but REI seems to have closed a lot of urban locations in particular.

17.07.2025 00:11 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

This speech and his farewell address give the impression of a very different presidency than actually elapsed between them.

23.06.2025 02:08 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0
The Chance for Peace - Wikisource, the free online library

It’s in the Chance for Peace speech. en.wikisource.org/wiki/The_Cha...

23.06.2025 02:04 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Of course, in model theory, we apply it to spaces that are not necessarily Polish (under the guise of Morley rank) and thus sometimes get "lolno" as a dimension out of pretty reasonable mathematical objects anyway.

14.06.2025 06:33 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Precisely. Hence countable for all Polish spaces, which is a nice kind of dimension to have.

14.06.2025 06:31 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 2    πŸ“Œ 0

Yes, although they're good ads for Cantor-Bendixson rank by comparison.

14.06.2025 06:24 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

I see. Then if you take a cone over a countable sequence of spaces with various countable-ordinal dimensions, you can probably get a larger countable-ordinal dimension.

14.06.2025 06:05 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

Does this mean the only infinite dimensions (given those assumptions) are omega and Ord?

14.06.2025 05:57 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

(There are a lot of model-theoretic dimensions that work this way.)

14.06.2025 05:48 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

I've not thought much about inductive dimension, but this much makes sense.

14.06.2025 05:47 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 2    πŸ“Œ 0

I'm always in the market for those - hit me.

14.06.2025 05:40 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

don't like that

14.06.2025 05:37 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

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