theorem
proved
tactic proof
locality_forces_additive_composition
show as:
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formal statement (Lean)
72theorem locality_forces_additive_composition
73 (L : UniformScaleLadder)
74 (additive_closure : L.levels 2 = L.levels 1 + L.levels 0) :
75 L.ratio ^ 2 = L.ratio + 1 := by
proof body
Tactic-mode proof.
76 have h0 : L.levels 0 ≠ 0 := ne_of_gt (L.levels_pos 0)
77 have h1 : L.levels 1 = L.ratio * L.levels 0 := L.uniform_scaling 0
78 have h2 : L.levels 2 = L.ratio * L.levels 1 := L.uniform_scaling 1
79 have h_sq : L.levels 2 = L.ratio ^ 2 * L.levels 0 := by
80 rw [h2, h1]; ring
81 have h_rhs : L.levels 2 = (L.ratio + 1) * L.levels 0 := by
82 rw [additive_closure, h1]; ring
83 have h_mul : (L.ratio ^ 2 - (L.ratio + 1)) * L.levels 0 = 0 := by
84 calc
85 (L.ratio ^ 2 - (L.ratio + 1)) * L.levels 0
86 = L.ratio ^ 2 * L.levels 0 - (L.ratio + 1) * L.levels 0 := by ring
87 _ = L.levels 2 - L.levels 2 := by rw [← h_sq, h_rhs]
88 _ = 0 := by ring
89 rcases mul_eq_zero.mp h_mul with hzero | hsize
90 · exact sub_eq_zero.mp hzero
91 · exact (h0 hsize).elim
92
93/-- **Bridge B1 (unconditional)**: from a zero-parameter scale ladder
94with additive composition, the scale ratio is forced to `φ`. -/