Recovery of low-rank Boolean moments from low degrees
Lax342547.MomentRecovery · concepts/Lax342547/MomentRecovery.lean · lax-342547
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Lemma
The rank obstruction in the second half of Lemma 5.2. A first nonzero selector moment of degree d produces an identity submatrix of size binomial(d, floor(d/2)). Consequently a Boolean moment matrix of rank at most r vanishes if all its moments of degree at most r vanish.
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| 1 | import Lax342547.MomentSpace |
| 2 | import Mathlib.LinearAlgebra.Matrix.Rank |
| 3 | |
| 4 | /-! |
| 5 | --- |
| 6 | title: Recovery of low-rank Boolean moments from low degrees |
| 7 | type: lemma |
| 8 | --- |
| 9 | The rank obstruction in the second half of Lemma 5.2. A first nonzero |
| 10 | selector moment of degree d produces an identity submatrix of size |
| 11 | binomial(d, floor(d/2)). Consequently a Boolean moment matrix of rank at |
| 12 | most r vanishes if all its moments of degree at most r vanish. |
| 13 | -/ |
| 14 | |
| 15 | namespace Lax342547.MomentRecovery |
| 16 | |
| 17 | open Lax342547.MomentSpace |
| 18 | |
| 19 | def IsSelectorHankel {Base : Type} {b degree : ℕ} |
| 20 | (w : Matrix (SelectorCoordinates b degree × Base) |
| 21 | (SelectorCoordinates b degree × Base) Binary) : Prop := |
| 22 | ∀ (S T U V : SelectorCoordinates b degree) (i j : Base), |
| 23 | S.val ∪ T.val = U.val ∪ V.val → w (S, i) (T, j) = w (U, i) (V, j) |
| 24 | |
| 25 | axiom eq_zero_of_rank_le {Base : Type} [Fintype Base] {b degree r : ℕ} |
| 26 | (w : Matrix (SelectorCoordinates b degree × Base) |
| 27 | (SelectorCoordinates b degree × Base) Binary) |
| 28 | (hH : IsSelectorHankel w) (hrank : w.rank ≤ r) |
| 29 | (hlow : ∀ (S T : SelectorCoordinates b degree) (i j : Base), |
| 30 | (S.val ∪ T.val).card ≤ r → w (S, i) (T, j) = 0) : w = 0 |
| 31 | |
| 32 | axiom eq_of_agree_low {Base : Type} [Fintype Base] {b degree r₁ r₂ : ℕ} |
| 33 | (w v : Matrix (SelectorCoordinates b degree × Base) |
| 34 | (SelectorCoordinates b degree × Base) Binary) |
| 35 | (hw : IsSelectorHankel w) (hv : IsSelectorHankel v) |
| 36 | (hrw : w.rank ≤ r₁) (hrv : v.rank ≤ r₂) |
| 37 | (hlow : ∀ (S T : SelectorCoordinates b degree) (i j : Base), |
| 38 | (S.val ∪ T.val).card ≤ r₁ + r₂ → w (S, i) (T, j) = v (S, i) (T, j)) : w = v |
| 39 | |
| 40 | end Lax342547.MomentRecovery |
| 41 |
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