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Model theory is the branch of mathematical logic which deals with the connection between a formal language and its interpretations, or models.

1 vote

Is there a metamathematical $V$?

This may be more in line with Vincent R.B. Blazy's answer, but one thing I would like to add is the principle of inexhaustibility. This principle appears in Maddy's "Believing the Axioms. I", where it …
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1 vote
Accepted

Minimal models in strong set theories - pt. 2

Negative answer for the first question: $L$ satisfies KP+"there exists a stable ordinal" but $L_\sigma$ does not. This is r.e. because "there exists a stable ordinal" can be expressed by a single axio …
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2 votes
0 answers
206 views

Some questions about the Hyperuniverse Program

The Hyperuniverse Program, founded by Sy D. Friedman, intends to produce new second-order axioms of set theory which appropriately formalize "the universe is maximal" in one of a few ways. A height-ma …
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6 votes

Smallest ordinal modelling $\aleph_1$?

About well-definedness of $X_1$, "being a model of ZFC" is definable since ZFC is a recursive theory, so we could construct some $\Sigma_1^0$ predicate $\textrm{isZFCAxiom}(e)$ for $e$ a Godel-coding …
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1 vote

How to solve this exercise about large countable ordinals?

This is a partial result, which is that there is an $(M,E)$ satisfying all but the end-extension requirement, in place of $M$ being an end-extension of $L_{\gamma_1}$, there is just an $X\subseteq M$ …
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3 votes

Parameter-free effective cardinals

Edit Jul 25: These results may be strengthenable by using theorem 7.8 of chapter V of Admissible Sets and Structures instead of lemma 1, I may edit this post in the future with any resulting improveme …
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