User Noah Schweber

16 votes

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Why is an object not defined as identity morphism?

answered Jul 19, 2019 at 18:48

16 votes

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How are Modal Logic and Graph Theory related?

answered Feb 3, 2013 at 20:19

16 votes

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Road to Solovay's Land.

answered Aug 11, 2012 at 1:53

16 votes

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Proof-Theoretic Ordinal of ZFC or Consistent ZFC Extensions?

answered Oct 5, 2013 at 20:24

16 votes

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Computable models of the ordinal numbers

answered Sep 9, 2019 at 2:52

15 votes

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Almost everywhere “filling” of the continuum by the first uncountable cardinal without CH

answered May 18, 2023 at 3:38

15 votes

Are there any undecidability results that are not known to have a diagonal argument proof?

answered Sep 6, 2023 at 17:30

15 votes

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What is the least inaccessible cardinal for Tarski-Grothendieck set theory?

answered Jan 28 at 20:06

15 votes

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Consistency of ZFC with inaccessible cardinals but no measurable cardinals

answered Oct 23 at 5:29

15 votes

Are integers conservatively embedded in the field of complex numbers?

answered 2 days ago

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Are the two meanings of "undecidable" related?

answered May 16, 2013 at 6:08

15 votes

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Does the statement 'there exists a first-order theory $T$ with no saturated models' have any set theoretic strength?

answered May 13, 2019 at 23:15

14 votes

Defining the standard model of PA so that a space alien could understand

answered May 23, 2019 at 5:16

14 votes

How do we formally construct the successor universe $\mathscr{U}^+$ of a universe $\mathscr{U}$ in $\mathsf{ZFC}$?

answered Nov 18, 2018 at 20:37

14 votes

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Let's keep adding once undecidable statements

answered Jun 13, 2016 at 19:22

14 votes

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Consistency of Analysis (second order arithmetic)

answered Mar 8, 2014 at 8:06

14 votes

Independence of the countable axiom of choice

answered Mar 14, 2015 at 20:38

14 votes

Infinitary logics and the axiom of choice

answered Jun 20 at 5:12

14 votes

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Is the power set axiom essential for constructing L?

answered Aug 14, 2019 at 9:22

14 votes

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Tarski's truth theorem — semantic or syntactic?

answered Apr 27, 2020 at 18:27

14 votes

How to understand the interface of the consistency strength hierarchy, reverse mathematics, and proof-theoretic ordinal analysis?

answered Mar 21, 2020 at 19:19

14 votes

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Who should be credited for the definition of rank in the von Neumann universe

answered Oct 11, 2020 at 0:55

13 votes

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Descriptive set theory for computer scientists?

answered Apr 7, 2021 at 14:57

13 votes

Special rational numbers that appear as answers to natural questions

answered Mar 2, 2020 at 21:31

13 votes

Is there an analog of Tennenbaum's theorem for real arithmetic?

answered Oct 18, 2019 at 16:57

13 votes

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Regarding Gentzen's note regarding 'Godel-points' (i.e., "Where is the Godel-point hiding?")

answered Oct 6, 2019 at 19:47

13 votes

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A doubt about the Gödel condensation lemma

answered Mar 4, 2022 at 1:25

13 votes

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How are real numbers defined in elementary recursive arithmetic?

answered Jun 14 at 19:50

13 votes

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Can we effectively axiomatize a theory that proves the negation of its own Gödel's sentence?

answered Sep 9, 2023 at 14:38

13 votes

Is it possible to define higher cardinal arithmetics

answered Nov 24, 2014 at 19:47

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478 Answers

Why is an object not defined as identity morphism?

How are Modal Logic and Graph Theory related?

Road to Solovay's Land.

Proof-Theoretic Ordinal of ZFC or Consistent ZFC Extensions?

Computable models of the ordinal numbers

Almost everywhere “filling” of the continuum by the first uncountable cardinal without CH

Are there any undecidability results that are not known to have a diagonal argument proof?

What is the least inaccessible cardinal for Tarski-Grothendieck set theory?

Consistency of ZFC with inaccessible cardinals but no measurable cardinals

Are integers conservatively embedded in the field of complex numbers?

Are the two meanings of "undecidable" related?

Does the statement 'there exists a first-order theory $T$ with no saturated models' have any set theoretic strength?

Defining the standard model of PA so that a space alien could understand

How do we formally construct the successor universe $\mathscr{U}^+$ of a universe $\mathscr{U}$ in $\mathsf{ZFC}$?

Let's keep adding once undecidable statements

Consistency of Analysis (second order arithmetic)

Independence of the countable axiom of choice

Infinitary logics and the axiom of choice

Is the power set axiom essential for constructing L?

Tarski's truth theorem — semantic or syntactic?

How to understand the interface of the consistency strength hierarchy, reverse mathematics, and proof-theoretic ordinal analysis?

Who should be credited for the definition of rank in the von Neumann universe

Descriptive set theory for computer scientists?

Special rational numbers that appear as answers to natural questions

Is there an analog of Tennenbaum's theorem for real arithmetic?

Regarding Gentzen's note regarding 'Godel-points' (i.e., "Where is the Godel-point hiding?")

A doubt about the Gödel condensation lemma

How are real numbers defined in elementary recursive arithmetic?

Can we effectively axiomatize a theory that proves the negation of its own Gödel's sentence?

Is it possible to define higher cardinal arithmetics