Two explicit Adian--Rabin constructions #
This file is the statement-level interface for the two constructions formalized in this project. The Miller--Tancer construction is generic in the number of generators and relators, subject to the normal-weight-one hypothesis. Gordon's Lemma 2.1 is generic in the host presentation and its abelian-order data.
theorem
Undecidability.AdianRabin.exists_miller_tancer_family
{n m : ℕ}
(P : FP n m)
(k : Fin n)
(hP : ¬ComputablePred P.wordProblem)
(hk : P.NormallyGenerates (Word.generator k))
:
∃ (A : ℕ → FP (n + 1) (m + 2)), FP.IsAdianRabinFamily A
The compressed Miller--Tancer construction produces an Adian--Rabin family with one additional generator and two additional relators when the normal generator is a displayed presentation generator.
theorem
Undecidability.AdianRabin.exists_gordon_family
{n m : ℕ}
(P : FP n m)
(condition : Gordon.Condition21 P)
(hP : ¬ComputablePred P.wordProblem)
:
∃ (A : ℕ → FP 2 (m + 1)), FP.IsAdianRabinFamily A
Gordon's Lemma 2.1 produces a two-generator Adian--Rabin family with one more relator than the host presentation.