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23 votes

Axiom of Computable Choice versus Axiom of Choice

As others have observed before, you cannot simply say "computable" and "ZF" in the same sentence without explaining what you mean. But I can tell you what your options are. In order to speak about co …
Andrej Bauer's user avatar
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9 votes

Elementary theory of the category of groupoids?

Robert Harper and Dan Licata studied the topic under the name 2-dimensional type theory, see their Canonicity for 2-Dimensional Type Theory and possibly these slides. As they are computer scientists t …
Andrej Bauer's user avatar
  • 48.8k
22 votes
Accepted

When does a topos satisfy the axiom of regularity?

The relationship between toposes and set theories was studied comprehensively in Steve Awodey, Carsten Butz, Alex Simpson, Thomas Streicher: Relating first-order set theories, toposes and categories …
Andrej Bauer's user avatar
  • 48.8k