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LeanPool.SmallUndecidableGroups.Host.ThetaCT

Restricting the first attaching map to ⟨t,c⟩ #

The isomorphism following Lemma 3.1 sends the copy of ⟨t,c⟩ in HMinus into Kc = ⟨t,c,k⟩. This file packages that restriction as a homomorphism whose source is the exact CT model used by the second compression stage.

Regard the exact ⟨t,c⟩ subgroup of the t-stage as a subgroup of HMinus, after applying the final-stage base embedding.

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    The restriction of the attaching isomorphism following Lemma 3.1 to the path base ⟨t,c⟩, with codomain enlarged to Kc = ⟨t,c,k⟩.

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      @[simp]
      theorem Undecidability.HostThetaCT.thetaCTtoKc_coe (datum : Thue.StandingDatum) (theta : HostYStage.ThetaData datum) (x : ↥(HostZBaseIntersections.CT datum)) :
      ↑((thetaCTtoKc datum theta) x) = ↑(theta.equiv ((ctToHMinus datum) x))

      Coercing the restricted map back to the ambient semantic Borisov group is literally the original attaching map following Lemma 3.1 on the corresponding element of HMinus.

      @[simp]

      The path generator t is sent to k.

      @[simp]

      The path generator c is fixed.