Draft — mutable and not usable as a dependency; its citation marks the draft state.

Proof of `The Post correspondence problem is undecidable`

groundedproofs/Lax251941Proofs/Results.lean · lax-251941

What this proof establishes

Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.

Read the Lean proof on GitHub

Description

The Post correspondence problem over N is undecidable: glued from the reduction and the undecidability of acceptance for tape machines, taken as assumptions.