theorem coordinationGap_pos {J_high J_low ρ : ℝ}
(hJl : 1 < J_low) (hJh : J_low < J_high) (hρ : ρ < 1) :
0 < coordinationGap J_high J_low ρ := by
simp only [coordinationGap, curvatureKReal]
have h1ρ : 0 < 1 - ρ := by linarith
have hJl_pos : 0 < J_low := by linarith
have hJh_pos : 0 < J_high := by linarith
rw [show (1 - ρ) * (J_high - 1) / J_high - (1 - ρ) * (J_low - 1) / J_low =
(1 - ρ) * ((J_high - 1) / J_high - (J_low - 1) / J_low) from by ring]
apply mul_pos h1ρ
rw [div_sub_div _ _ (ne_of_gt hJh_pos) (ne_of_gt hJl_pos)]
apply div_pos
· nlinarith
· exact mul_pos hJh_pos hJl_posCore definitions for the Lean formalization of Paper 1c: