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For question in Proof Theory, where "proofs" themselves are the object of mathematical investigation. It is not to be used to request a proof of some result.

7 votes
0 answers
234 views

Unprovable integer identity involving exponentiation

I was thinking about Tarski's problem, and was wondering what happens if we have a theory $T$ with two sorts $N,Z$ with intended interpretations $\def\nn{\mathbb{N}}$$\def\zz{\mathbb{Z}}$$\nn,\zz$ res …
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7 votes
1 answer
244 views

Independent/Easy fraction of sentences over PA

Let $S(n)$ be the set of all sentences over PA of length at most $n$ (counting the quantifier symbols, boolean connectives, arithmetic operations and constants, and counting each variable as length $1 …
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  • 2,912
4 votes
0 answers
159 views

Can this theory of dyadic rationals prove that multiplying by three is the same as summing t...

(This question arose from a discussion with Jade Vanadium about a theory of dyadic rationals.) Let $T$ be the 2-sorted FOL theory with sorts $ℕ,ℚ$ and constant-symbols $0,1$ and binary function-symbol …
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4 votes
1 answer
364 views

Does ACA prove categoricity of the reals?

$\def\f#1{\text{#1}}$Does $\f{ACA}$ prove that any two internally complete ordered fields are isomorphic? Here internal completeness is expressed roughly as "every sequence of reals with an upper boun …
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