Registry · Definition V.D195 tau-effective formalized

V.D195 — Primordial He-4 Mass Fraction

Y_p = 20/81 = (8/27)(5/6) = 0.24691..., matching Planck 2018 at 0.43 sigma.

Book V Part 6 Ch. 48

Dependency Graph

Depends on (2)

V.D192 V.D194

Depended on by (5)

V.D196 V.D307 V.R324 V.T148 V.T150

Lean Formalization

Module: TauLib.BookV.Cosmology.HeliumFraction

Symbol: HeliumPrediction