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A Certifying Proof Assistant for Synthetic Mathematics in Lean

Talkat CPP 2026 · 2026-01-12..01-13· [large-language-models]
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name:Yiming Xu
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SynthLean embeds a deep embedding of Martin-Löf type theory as a DSL inside Lean and implements certifying normalization-by-evaluation typechecking that emits Lean proof terms the kernel verifies. The project formalizes syntax (universes, Π, Σ, identity types, axiomatized constants), formalizes natural model semantics and proves soundness, and ships a workflow where constructions live either internally in MLTT or externally in semantic models; inductive/HITs are not yet supported but artifacts and code are available.

AI-written summary · about

  1. 0:00Introduction
  2. 0:21Synthetic mathematics
  3. 3:14Synthetic vs analytic math
  4. 5:21Goals of the assistant
  5. 7:29Syntax of type theory
  6. 9:58Categorical semantics
  7. 12:05Implementation
  8. 16:41Challenges in formalization
  9. 17:22Future directions
  10. 17:44Q&A
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