A Complex-Valued Spacetime Metric: Derivations of Quantum Mechanics, Electromagnetism, Entropy, and Predictions for the Hubble Tension

v1 (March 8, 2026): Initial deposit.

v2 (March 9, 2026): Adds three new sections — the complex S-matrix formalism replacing five QM postulates with derived results; dark energy identified as residual quantum interactions with equation of state w₀ = −1.057 (parameter-free prediction from ε₀ alone); and constrained decoherence as the mechanism for galaxy rotation curves, predicting v_flat ≈ 191 km/s from ε₀ without free parameters or dark matter halos. Two new verification figures added: Fig_Q_verification.png and Fig_OmegaLambda_check.png.