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8
Reverse mathematics below RCA
6
First-order vs second-order provability
3
Existential instantiation in Hilbert-style deduction systems
4
Subscript 0 in Reverse Mathematics
3
Is there a general setting for self-reference?
15
Second-order term in first-order logic?
3
Does higher order arithmetic interpret the axiom of choice?
7
Z_2 versus second-order PA
21
What is “Seetapun Enigma”?
7
Can infinity shorten proofs a lot?
5
Explicit expression for recursively defined functions
0
Undecidability [sic] in set theory [per se]
11
Up-to-date version of Principia Mathematica?
3
“local variables” in first-order formulas
13
Formalizing Euclid’s proof of the infinitude of primes
1
Variant of the usual proof method for undecidability of the halting problem
27
What’s a magical theorem in logic? (2)
8
True by accident (and therefore not amenable to proof)
13
Notion of Truth and Axioms
7
ZFC, set membership and FOL
2
What sets are “decidable from competing provers”?
7
The Reverse Mathematics of writing a set as a union?
3
truth vs. provability for ordered fields
8
Most ‘unintuitive’ application of the Axiom of Choice?
17
Undecidable theories easier than $Q$
10
Completeness vs Compactness in logic
4
Going to graduate school for mathematics next year, need some advice
2
Models of computation with decidable halting problem?
3
Proofs that use Infinite/Finite Priority Injury Method
7
Prenex normal form vs. quantifier rank
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