OAI/GroupTheory/PolycyclicRecognition/Geometry/DiscreteNilpotentLieGroup.lean

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Discrete subgroups of simply connected nilpotent Lie groups

Nilpotence makes every adjoint operator have only the zero generalized weight. A simultaneous triangular basis therefore has zero height, and the discrete height-kernel theorem applies to the whole group.

  1. theorem OAI.PolycyclicRecognition.nonempty_triangularAdjoint_of_nilpotent line 21

    Source documentation

    Engel nilpotence supplies the split adjoint basis needed by the concrete height-kernel argument.

    theorem nonempty_triangularAdjoint_of_nilpotent (L : Type*)
        [LieRing L] [LieAlgebra ℝ L] [FiniteDimensional ℝ L] [LieRing.IsNilpotent L] :
        ∃ n : ℕ, Nonempty (TriangularAdjoint L n) := by
    …

    Mentions: OAI.PolycyclicRecognition.TriangularAdjoint

  2. theorem OAI.PolycyclicRecognition.isPolycyclic_discrete_nilpotent_lieGroup line 40

    Source documentation

    Every discrete subgroup is polycyclic; finite generation is a conclusion.

    theorem isPolycyclic_discrete_nilpotent_lieGroup
        [LieRing.IsNilpotent (GroupLieAlgebra (𝓘(ℝ, E)) G)]
        (Γ : Subgroup G) [DiscreteTopology Γ] : IsPolycyclic Γ := by
    …

    Mentions: OAI.PolycyclicRecognition.IsPolycyclic