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Upsilon

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formal statement (Lean)

  26noncomputable def Upsilon (P : ILG.KernelParams) (a : ℝ) : ℝ :=

proof body

Definition body.

  27  if a ≤ 0 then 1 else 1 + P.C * a ^ P.alpha
  28
  29/-- The modified Sachs focusing equation (Target G).
  30    For angular diameter distance D_A along an affine parameter λ:
  31    d²D_A/dλ² + (1/2) * Upsilon(a) * R_μν k^μ k^ν * D_A = 0
  32    where Ricci focusing is rescaled by Upsilon. -/

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