Paired-frame orbit under the primal and dual actions
Lax342547.PairedFrames · concepts/Lax342547/PairedFrames.lean · lax-342547
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Theorem
Lemma 4.1: two individually injective pairs of frames with equal Gram pairings differ by one ambient linear automorphism, acting contragrediently on the dual frame. No nondegeneracy of the prescribed Gram is needed.
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| 1 | import Mathlib.LinearAlgebra.Dual.Lemmas |
| 2 | import Mathlib.LinearAlgebra.Matrix.ToLin |
| 3 | |
| 4 | /-! |
| 5 | --- |
| 6 | title: Paired-frame orbit under the primal and dual actions |
| 7 | type: theorem |
| 8 | --- |
| 9 | Lemma 4.1: two individually injective pairs of frames with equal Gram |
| 10 | pairings differ by one ambient linear automorphism, acting contragrediently |
| 11 | on the dual frame. No nondegeneracy of the prescribed Gram is needed. |
| 12 | -/ |
| 13 | |
| 14 | namespace Lax342547.PairedFrames |
| 15 | |
| 16 | universe u v w z |
| 17 | |
| 18 | variable {K : Type u} {U : Type v} {V : Type w} {W : Type z} [Field K] |
| 19 | [AddCommGroup U] [Module K U] |
| 20 | [AddCommGroup V] [Module K V] [hVdim : FiniteDimensional K V] |
| 21 | [AddCommGroup W] [Module K W] |
| 22 | |
| 23 | axiom paired_frame_orbit {K : Type u} {U : Type v} {V : Type w} {W : Type z} [Field K] |
| 24 | [AddCommGroup U] [Module K U] |
| 25 | [AddCommGroup V] [Module K V] [FiniteDimensional K V] |
| 26 | [AddCommGroup W] [Module K W] |
| 27 | (A A' : U →ₗ[K] V) (B B' : W →ₗ[K] Module.Dual K V) |
| 28 | (hA : Function.Injective A) (hA' : Function.Injective A') |
| 29 | (hB : Function.Injective B) (hB' : Function.Injective B') |
| 30 | (hgram : ∀ u w, B w (A u) = B' w (A' u)) : |
| 31 | ∃ L : V ≃ₗ[K] V, (∀ u, L (A u) = A' u) ∧ |
| 32 | ∀ w v, B w (L.symm v) = B' w v |
| 33 | |
| 34 | axiom paired_matrix_orbit {I J N : Type} [Fintype I] [Fintype J] [Fintype N] |
| 35 | [DecidableEq N] (A A' : Matrix N I K) (B B' : Matrix N J K) |
| 36 | (hA : Function.Injective A.mulVec) (hA' : Function.Injective A'.mulVec) |
| 37 | (hB : Function.Injective B.mulVec) (hB' : Function.Injective B'.mulVec) |
| 38 | (hgram : A.transpose * B = A'.transpose * B') : |
| 39 | ∃ C D : Matrix N N K, C * D = 1 ∧ D * C = 1 ∧ |
| 40 | C * A = A' ∧ D.transpose * B = B' |
| 41 | |
| 42 | end Lax342547.PairedFrames |
| 43 |
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