List questions from model-theory | MathQa

Infinite, finite and arbitrarily large models.

Published on 29 Dec 2024 - 11:32

What's the difference between a model and a $\sigma$ structure?

Published on 31 Dec 2024 - 14:38

How it can be formally proved that a formula of First Order Logic with identity has only infinite models?

Published on 11 Jan 2025 - 0:26

Showing that a certain formula of second order logic with full semantic is true in all and only non-standard model of arithmetic.

Published on 05 Jan 2025 - 7:11

For $\mathbb{N}$ a structure in $\mathcal{L}=\{s, 0, 1\}$, are the sum and product definable?

Published on 29 Dec 2024 - 13:11

$R \subseteq M^I$ is $A$-invariant, then $R$ is $A$ definable in the next two infinitary logics.

Published on 28 Dec 2024 - 1:28

Using the compactness theorem to prove Principal ideal rings nonaxiomatizable

Published on 28 Dec 2024 - 13:50

Proving that every interval in an o-minimal structure is definably connected.

Published on 01 Jan 2025 - 21:41

Is there a countable transitive model satisfying the same set of first-order sentences as $V$?

Published on 03 Jan 2025 - 0:48

restriction map in Stone space is open

Published on 10 Jan 2025 - 23:32