Derives BA = sqrt (3) /2 = cos (pi/6) from the (2, 1) Lorentzian signature of the Eckert manifold via spin-1/2 representation theory of SL (2, R). Nine-step derivation chain, each link a theorem or proven result. Signature determines microstate count (N=4), Fisher simplex angle (pi/3), and forces cos (theta/2) as unique Wigner amplitude. 6/6 kill conditions PASS. Error vs empirical: 0. 11%. Framework now has zero free parameters.
Anthony W. Eckert (Wed,) studied this question.