Factorization and counting of low-rank binary matrices
Lax342547.LowRankCounting · concepts/Lax342547/LowRankCounting.lean · lax-342547
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Theorem
A rank-at-most-r matrix factors through r coordinates. Counting the two factors gives the rectangular low-rank estimate used for binary mixer tests, including the alternating off-diagonal block argument.
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| 1 | import Lax342547.MomentSpace |
| 2 | import Mathlib.LinearAlgebra.Matrix.Rank |
| 3 | import Mathlib.Probability.Distributions.Uniform |
| 4 | |
| 5 | /-! |
| 6 | --- |
| 7 | title: Factorization and counting of low-rank binary matrices |
| 8 | type: theorem |
| 9 | --- |
| 10 | A rank-at-most-r matrix factors through r coordinates. Counting the two |
| 11 | factors gives the rectangular low-rank estimate used for binary mixer |
| 12 | tests, including the alternating off-diagonal block argument. |
| 13 | -/ |
| 14 | |
| 15 | namespace Lax342547.LowRankCounting |
| 16 | |
| 17 | axiom factorization {K I J : Type} [Field K] [Fintype I] [Fintype J] |
| 18 | (M : Matrix I J K) (r : ℕ) (hr : M.rank ≤ r) : |
| 19 | ∃ X : Matrix I (Fin r) K, ∃ Y : Matrix (Fin r) J K, X * Y = M |
| 20 | |
| 21 | open Lax342547.MomentSpace |
| 22 | open scoped ENNReal |
| 23 | |
| 24 | axiom card_low_rank {I J : Type} [Fintype I] [Fintype J] (r : ℕ) : |
| 25 | Nat.card {M : Matrix I J Binary // M.rank ≤ r} ≤ 2 ^ ((Fintype.card I + Fintype.card J) * r) |
| 26 | |
| 27 | axiom uniform_low_rank_bound {I J : Type} [Fintype I] [Fintype J] [DecidableEq I] [DecidableEq J] |
| 28 | (r : ℕ) : (PMF.uniformOfFintype (Matrix I J Binary)).toOuterMeasure {M | M.rank ≤ r} ≤ |
| 29 | (2 : ℝ≥0∞) ^ ((Fintype.card I + Fintype.card J) * r) / 2 ^ (Fintype.card I * Fintype.card J) |
| 30 | |
| 31 | end Lax342547.LowRankCounting |
| 32 |
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