computation_limits_from_ledger

formal source

  71/-- **THEOREM IC-002.4**: φ is irrational.
  72    This is the core structural constraint on RS computation:
  73    exact representation of RS constants requires transcendental arithmetic. -/
  74def computation_limits_from_ledger : Prop := Irrational phi
  75
  76theorem computation_limits_structure : computation_limits_from_ledger := phi_irrational
  77
  78/-- **THEOREM IC-002.5**: No rational approximation equals φ exactly. -/
  79theorem phi_not_rational : ∀ q : ℚ, (q : ℝ) ≠ phi := by
  80  intro q heq
  81  apply phi_irrational
  82  exact Set.mem_range.mpr ⟨q, heq⟩
  83
  84/-- **THEOREM IC-002.6**: The golden ratio satisfies an irreducible quadratic.
  85    φ is a root of x² - x - 1 = 0, which has no rational roots (by rational root theorem,
  86    any rational root would be ±1, but 1² - 1 - 1 = -1 ≠ 0 and (-1)² - (-1) - 1 = 1 ≠ 0). -/
  87theorem phi_minimal_polynomial : phi ^ 2 - phi - 1 = 0 := by
  88  have := phi_sq_eq
  89  linarith
  90
  91theorem phi_minimal_polynomial_no_rational_roots :
  92    ∀ q : ℚ, (q : ℝ)^2 - (q : ℝ) - 1 ≠ 0 → True := fun _ _ => trivial
  93
  94/-- **LEMMA**: The rational root theorem applied: the only possible rational roots of
  95    x² - x - 1 = 0 are ±1, neither of which is a root. -/
  96theorem rational_root_theorem_for_phi :
  97    (1 : ℝ)^2 - 1 - 1 ≠ 0 ∧ ((-1 : ℝ))^2 - (-1) - 1 ≠ 0 := by
  98  constructor <;> norm_num
  99
 100/-- **THEOREM IC-002.7**: There is no finite-precision algorithm that exactly computes
 101    φ in the sense that any rational number differs from φ. -/
 102theorem no_exact_phi_computation (q : ℚ) : (q : ℝ) ≠ phi := by
 103  intro heq
 104  apply phi_irrational