Condensed Type Theory
- š¤ Speaker: Dr Johan Commelin (Utrecht University) š Website
- š Date & Time: Thursday 02 May 2024, 17:00 - 18:00
- š Venue: Live-streamed at MR14 Centre for Mathematical Sciences
Abstract
Condensed sets form a topos, and hence admit an internal type theory. In this talk I will describe a list of axioms satisfied by this particular type theory. In particular, we will see two predicates on types, that single out a class CHaus of “compact Hausdorff” types and a class ODisc of “overt and discrete” types, respectively. A handful of axioms describe how these classes interact. The resulting type theory is spiritually related Taylor’s “Abstract Stone Duality”.
As an application I will explain that ODisc is naturally a category, and furthermore, every function ODisc ā ODisc is automatically functorial. This axiomatic approach to condensed sets, including the functoriality result, are formalized in Lean 4. If time permits, I will comment on some of the techniques that go into the proof.
Joint work with Reid Barton.
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Series This talk is part of the Formalisation of mathematics with interactive theorem provers series.
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Dr Johan Commelin (Utrecht University) 
Thursday 02 May 2024, 17:00-18:00