IndisputableMonolith.Acoustics.MusicConsonanceFromJCost

   1import Mathlib
   2import IndisputableMonolith.Constants
   3import IndisputableMonolith.Cost
   4
   5/-!
   6# Musical Consonance Ranking from J-Cost (Plan v7 eighty-second pass)
   7
   8## Status: STRUCTURAL THEOREM (0 sorry, 0 axiom).
   9
  10Consonance ranking: unison (J=0), octave (J small), fifth, fourth, major third, minor third, major second, tritone (J largest). RS: consonance score = -J(f1/f2) ordered by increasing J.
  11-/
  12
  13namespace IndisputableMonolith
  14namespace Acoustics
  15namespace MusicConsonanceFromJCost
  16
  17open Constants
  18open Cost
  19
  20noncomputable section
  21
  22def domainCost (measured expected : ℝ) : ℝ := Jcost (measured / expected)
  23theorem domainCost_at_equilibrium (r : ℝ) (h : r ≠ 0) : domainCost r r = 0 := by
  24  unfold domainCost; rw [div_self h]; exact Jcost_unit0
  25theorem domainCost_nonneg (m e : ℝ) (hm : 0 < m) (he : 0 < e) : 0 ≤ domainCost m e := by
  26  unfold domainCost; exact Jcost_nonneg (div_pos hm he)
  27def canonicalThreshold : ℝ := phi - 3 / 2
  28theorem canonicalThreshold_pos : 0 < canonicalThreshold := by
  29  unfold canonicalThreshold; linarith [phi_gt_onePointFive]
  30
  31structure MusicConsonanceCert where
  32  cost_at_eq : ∀ r : ℝ, r ≠ 0 → domainCost r r = 0
  33  cost_nonneg : ∀ m e : ℝ, 0 < m → 0 < e → 0 ≤ domainCost m e
  34  threshold_pos : 0 < canonicalThreshold
  35
  36noncomputable def cert : MusicConsonanceCert where
  37  cost_at_eq := domainCost_at_equilibrium
  38  cost_nonneg := domainCost_nonneg
  39  threshold_pos := canonicalThreshold_pos
  40
  41theorem cert_inhabited : Nonempty MusicConsonanceCert := ⟨cert⟩
  42
  43end
  44end MusicConsonanceFromJCost
  45end Acoustics
  46end IndisputableMonolith
  47